Note that even though this was originally posted in 2008, the articles get regular review and updates to keep them current.

EVERYTHING YOU WANTED TO KNOW ABOUT ELECTRIC POWERED FLIGHT
An E-Book by Ed Anderson
Updated March 2015

PREFACE

A number of people have suggested I write a book on the topic of electric flight. I would, but I find the electric field is changing too fast. Paper based books go out of date too quickly. Instead I am going to create a thread that is my version of an e-book on the subject of electric powered flight. This e-format allows me to provide updates and to answer questions, things I can't do in paper form.

Whether you are a new flyer, a wet fuel pilot, or a glider pilot who wants to add an electric motor to your glider, I hope you find value here. Of course, I will fail to live up to the title as you can't know everything, but I will try to hit the essentials. I am also going to provide an index for your convenience.

The principals of weight, lift, drag, stall and all the other things we know about flying apply the same regardless of what motor or engine the plane may have. The power systems may differ, and each has its unique benefits and quirks, but the principles of flight remain the same.

For new pilots who have no background, just relax, breath deeply and read. I have tried to put it all in one place for you. Don't expect to know it all in one reading. After you take your early flights, come back and read again as you will now have some real life experience to compare to what is contained here.

If you are starting with an RTF electric airplane, you really don't need to know all this stuff. However be sure to look at the articles on RTFs and the Six Keys to Success for New Pilots. I think you will find them helpful.

For wet fuel pilots coming into electric, the first problem is terms and their meanings. The first two articles are specifically focused on this need.

I want to change your question from "What is the electric equivalent of a .40 glow engine?” to "What electric power system would be right for a 40 size glow plane?" The first question is VERY hard to answer, the second is not. I am going to ask you to put aside what you know of wet fuel systems and look at electric power with a fresh mind.

Electric motor systems are both simpler and more complex than wet fuel systems. It is just a matter of looking at them in terms that make sense for electric power and not trying to make them fit the wet fuel framework.

What about batteries? How do I choose between NiCd, NiMh, Lipo, and others? We will cover that.

Battery chargers are a mystery too, yet they are an integral part of electric flight. We will cover those.

What about tools to tell what is going on in your electric power system? Yes, we will cover that also.

I will be adding new chapters and topics, so visit again, you might see a new topic that interests you. And don't hesitate to suggest topics that need to be covered.

I invite others who have experience in this area to add their knowledge and become co-authors of this e-book. If you have an area of expertise, share it with us. If you come across a good discussion or a reference source somewhere, post a link to it and tell us why you found it helpful.

You will find my articles and posts rich in links to other resources. Be sure to take a look.

If you have a question, by all means ask as others will have the same question.

I hope you find this helpful. I hope you will contribute your knowledge as well.

As the book has progressed, I have expanded the range of the discussion beyond strictly electric topics but I have tried to stay within those topics that I feel are are relevant to electric flyers. For example the electric "parkflyer" class of planes has a large number of rudder/elevator/throttle planes. As pilots move from 2 or 3 channels to 4 channel planes sometimes people get confused as to were the rudder should reside on the radio. The article at post 27 addresses this question.

Post 139 addresses a question that comes up over and over related to kV. and 170 talks to the subject of picking your first radio. Note that this is slanted to electric and glider pilots more so than to glow or gas pilots but the content should be of interest to any new pilot.

Looking back, I would have organized the chapters/articles in a different order, but I am not going to trash the thread to do it, so I hope you will not find it too confusing as it appears here.

This book also appears on www.wattflyer.com. The chapters are the same but their numbers are different as the discussion has progressed differently over there.

This brief discussion is intended to clear up a few terms and concepts
around electricity as it applies to electric airplanes.

Think of electricity like water. Volts = pressure Amps = flow

Volts is like pounds per square inch, psi. Says nothing about how much
water is flowing, just how hard it is being pushed. You can have 100 psi
with zero water flow if the cap is on the hose.

Amps is flow, like gallons per hour. You can have flow at low pressure and
you can have flow at high pressure.

Amp hours is how much flow can be sustained for how long. It is used as a
way of measuring how much electricity is in the battery. Like how many
gallons of gas in your tank. It is a capacity number. Says nothing about
flow or pressure, it is about capacity.

Amps and mili amps? We are just moving the decimal point around.

1 amp (short for ampere) = 1000 miliamps (mili means 1/1000 amps)

Examples

So a 7 cell NIMH or NICD pack provides 8.4V (pressure).

The motor will draw electricity from the pack at a certain flow rate, or
amps.

If you have a 650 mili amp hour pack, it can deliver a flow of .650
amps (650 miliamps) for one hour. If you draw it out faster, it
doesn't last as long. So your motor might pull 6.5 amps for 1/10 of an
hour, or about 6 minutes.

A 1100 mah pack has double the capacity of the 650 mah pack, so it should
last "about" twice as long.

What is C in relation to batteries?

C ratings are simply a way of talking about charge and discharge rates for
batteries. How fast can you charge them and how fast can you discharge them.

1C, = 1 time the rated mah capacity of the battery. So if you charge your
650 mah pack at 1C, you would be charging it at 650 miliamps, or .650 amps.

1C on a 1100 pack would be 1.1 amps.

2 C on your 1100 pack would be 2.2 amps

Motor batteries are often rated in Discharge C and charge C.

So a 1100 mah pack (1.1 amp hour) might be rated for 10C discharge, so you
can pull 11 amps ( flow ) without damaging the battery.

Then it might be rated at 2C charge rate (flow), so you charge it at 2.2
amps (2200 mah)

How did I do? Things clearing up?

If you have a 500 mah pack - any kind - and it is rated at 16C that means it
can deliver 8 amps.

If you have a 1000 mah pack - any kind - and it is rated at 8C that means it
can deliver 8 amps.

If you have a 1000 mah pack - any kind - and it is rated at 12C that means
it can deliver 12 amps

If you have a 1500 mah pack - any kind - and it is rate at 8C that means it
can deliver 12 amps

If you have a 1500 mah pack - any kind - and it is rated at 20 C that means
it can deliver 30 amps.

If you have a 3000 mah pack - any kind - and it is rated at 10 C that means
it can deliver 30 amps.

So, if you need 12 amps you can use a pack with a higher C rating or a pack
with a higher mah rating to get to needed amp delivery level.

One last point. Motor batteries vs. receiver batteries

Some batteries can sustain high discharge rates. Others can not.

Those used as transmitter/receiver packs typically are made for low flow/amp
rates while those made for motor packs can sustain higher rates.

Having a 600 mah pack does not tell you if it is a motor pack that can put
out 6 amps, or if it is a transmitter/receiver pack that would be damaged if
you tried to pull power at 6 amps. It is enough to say that they are
different.

Clearly a motor pack could be used for a transmitter/receiver job, but a
transmitter/receiver pack should not generally be used as a motor pack.

It is best to size your battery packs so they run somewhat below their
maximum C rating. You will stress them less and they will last longer. For
example, if your motor needs a pack that can deliver 10 amps, getting a 1000
mah pack that is rated for 10C ( 10 amps ) will meet the spec, but it is
running at its limit. A 15 C rated 1000 mah pack would be better, or
perhaps a 1300 mah 10 C pack. In either of these cases, the pack will be
less stressed and should handle the load much better over the long term.

MotoCalc
MotoCalc will tell you everything you need to know: Amps, Volts, Watts, RPM,
Thrust, Rate of Climb, and much more! It is a popular tool for predicting
the proper motor, prop, battery pack for electric planes.http://www.motocalc.com/

SIZING POWER SYSTEMS FOR
ELECTRIC AIRPLANES
by Ed Anderson
aeajr on the
forums
Revised
March 2015

This may get a little technical but I will try to keep it as simple as I
can. I will draw parallels to cars and bicycles in many places as most
people can relate to these and know at least a little about how they work.

I will use round numbers where I can and will use some high level examples.
If you are an engineer you will see that I am taking some liberties here for
the sake of simplicity. I will go through the parts of the power system,
then, toward the end, I will show you how we tie these all together to come
up with a complete power system.

POWER = WATTS

I will be using the terms Volts, Amps and Watts throughout this discussion.
Let me define them.

Volts = the pressure at which the electric energy is being delivered - like
pounds per square inch or PSI in a fuel system or water from a garden hose.

Volts is about pressure, it says nothing about flow. You will see volts
abbreviated as V.

Amps = the quantity or flow of electricity being delivered, like gallons per
minute in a fuel system or that same garden hose. Amps is about flow, it
says nothing about pressure. You will see amps abbreviated as A.

Watts = V X A. This is a
measure of the energy or power being delivered.
This is how we measure the ability of that electricity to do work, in our
case the work of turning a propeller to move our airplane through the air.

Watts is about both pressure and flow. This serves the same purpose as
the horsepower rating of your car's engine. In fact 746 watts = 1
horsepower. So if you had an electric car, the strength of its motor could
be reported in either watts or horsepower. You will see watts abbreviated as
W.

Whether brushed orbrushless, the motor's job is to convert electricity into
mechanical motion to turn the propeller to move air. Efficiency is how we
measure how much of the power, the watts, that our battery delivers to the
motor is actually turned into useful work and how much is wasted as heat.
A higher efficiency motor delivers more energy to the prop, and wastes
less.

A typical brushed motor, say a speed 400, is only about 40-50% efficient.
Only about half the watts delivered to the motor actually end up as usefulwork turning the propeller.
The rest is wasted. Motors that have a "speed"designation, like speed
400, are brushed motors. There are other names forbrushed motors but the
"speed" term is a common one. They are inexpensive
and they work. For example, you can buy a speed 400 motor and electronic
speed control, ESC, for $20. A comparable brushless motor/ESC combination
would likely be 2 to 4 times that much, but prices have been coming down fast.

Brushed motors used to be more common in RC airplanes however with price
drops over the past few years brushless motors have become the standard with
brushed motors typically only seen in micro planes.

Brushless motors tend to be more efficient. They typically deliver 70-90%
of that input power to the propeller, Thus you get better performance per
watt with brushless motors. Seen a different way, if you use a brushless
motor, then, for the same flying performance you will use less energy which
means your battery will last longer. Or you can use a smaller size and
weight brushless motor/battery combo to get comparable performance
because the motor turns more of the watts from the battery into useful work
of turning the propeller.

As with many decisions we make, this is a cost benefit decision. Am I
willing to pay more to get more? That is up to you.

THE BATTERY IS MORE THAN
JUST THE FUEL TANK

Think of the battery as the fuel tank plus the fuel pump and a supercharger
all rolled into one. It feeds/pushes energy to the motor. So you have to
look at the battery and the motor as one unit when you are sizing power
systems for electric planes. In many cases we start with the battery when
we size our systems because the motor can't deliver the power to the prop if
the battery can't deliver the power to the motor.

The higher the voltage rating of the battery, the higher the pressure, like
a supercharger on a car engine. More pressure delivers more air/fuel
mixture to the engine which allows the engine to produce more power to turn
the wheels of the car.

Higher voltage pushes more electricity into the motor to produce more power,
IF AND ONLY IF, the battery has the ability to deliver more electricity.
Again using the car analogy, if you put a big motor in a car and put a tiny
fuel line and a weak fuel pump, the motor will never develop full power. In
fact the motor might starve and stall once you got past idle. Such is the
same with batteries. We need voltage, we need capacity, but we also need to
know how many amps the battery is capable of delivering at peak.

If we compare an 8 cell AAA
battery pack to an 8 cell C battery pack we get
9.6 V for both packs. However the AAA pack may only be able to deliver 6
amps. After that the cells will heat up and either be damaged or the
voltage will start to drop fast. The C pack, also 9.6 V, might be able to
deliver 60 amps without damage. So we have to size not only by voltage, but
by the ability to deliver amps to the motor. Again, think of the fuel line
and the fuel pump as your image of what I am trying to explain. If the
motor needs 12 ounces of fuel per minute to run but the fuel line can only
deliver 8, the engine will starve and die.

Using our electric motors, a given motor may want to draw 10 amps
( the quantity of electricity flowing ) at 8.4 volts ( the pressure at which
the electricity is being delivered) to spin a certain propeller. We would
say that the battery is delivering, or that the motor is drawing 84 watts,

i.e.: 8.4V x 10A. If you bump up the voltage to 9.6 volts, the motor will
try to spin faster which will turn the prop faster. In order to do this the
motor will draw and the battery must deliver more amps into the motor, more
energy to the motor, which will produce more power to the propeller but it
will also produce more heat in the motor. In this example, if we move from
an 8.4V battery pack to a 9.6V battery pack the motor may now take 14 amps.
But can this particular electric motor handle 14 amps? Can the electronic
speed control handle 14 amps?

If you bump up the pressure too much, you can break something.
Putting a big supercharger on an engine that is not designed for it will
break parts of the engine. Too much voltage can over power your electric
motor and damage it. So there is a balance that has to be struck.
Different motors can take different amounts of power, watts, volts X amps,
without damage. For example, a speed 400 motor might be fine taking 10 amps
at 9.6 volts or 96 watts. However bump it up to 12 volts, while spinning
the same prop, and it might draw 18 amps which could burn it out.

Our goal is a balanced power system. If you match the right battery with
the right motor, you get good performance without damage to the motor. In
many cases airplane designers will design planes around a specific
motor/battery combination so that they match the size and weight of the
plane to the power system for good performance.

kV - REVOLUTIONS PER VOLT -

An important fact about electric motors is that they tend to want to spin
at a certain speed for every volt that we apply to them. We won't go into a
lot of depth here, but it is important to understand that if you apply 5
volts to a motor, it will try and spin at a given speed. If you apply 10
volts it will try to turn twice as fast. This fact is noted on the specs of
your motor in the form of the kV rating. Basically a kV rating of 1000
means that the motor will spin at 1000 RPMs for every volt applied.

If you apply 10 volts, it will try to spin at 10,000 rpms. It will try to
achieve this RPM level regardless of the load we put on it. It will draw
more and more amps from the battery trying to hit this number.

By boosting the voltage on a motor, and getting it to spin faster we can get
it to produce more power, but we must be careful not to over work the motor.
Even if it is 80% efficient, 20% of the power that goes into it turns into
heat. Too much heat can melt insulation, cause shafts to expand in bearings
and all sorts of bad things can happen. So, as we change the voltage we
apply to our airplane motors we sometimes change the propeller
too.

PROPELLERS

Propellers are sized by diameter and pitch.
The diameter of the propeller determines the volume of air the propeller
will move, producing thrust, or pushing force. Roughly speaking the
diameter of the propeller will have the biggest impact on the size and
weight of the plane that we can fly. Larger, heavier planes will typically
fly better with larger diameter propellers.

Pitch refers to the angle of the propeller blade and refers to the distance
the propeller would move forward if there were no slippage in the air. So a
7 inch pitch propeller would move forward 7 inches per rotation, if there
were no slippage in the air. If we combine pitch with the rotational speed
of the propeller we can calculate the pitch "speed" of the propeller. So,
at 10000 revolutions per minute, that prop would move forward
70,000 inches per minute. If we do the math, that comes out to a little
over 66 miles per hour.

By changing the diameter and the pitch of the propeller we can have a
similar effect to changing the gears in your car or a bicycle. It will be
harder for your motor to turn a 9X7 propeller than an 8X7 propeller. And
it would be harder to turn a 9X7 propeller than a 9X6 propeller. The
larger or steeper pitched propellers will require more energy, more watts,
more horsepower, to turn them. Therefore we need to balance the diameter
and pitch with the power or wattage of the motor/battery system.

Fortunately we don't actually have to do this ourselves as motor
manufacturers will often publish suggestedpropellers to use with a
given motor/battery combination. We can use these
as our starting point. If we want we can try different propellers that are
near these specifications and use a wattmeter to measure the results. More
on wattmeters later.

GEARBOXES

While unusual on glow or gas planes, gearboxes are common on electric
planes. Their primary function is similar to the transmission on a car. The
greater the gear ratio, the higher the numerical value, the slower the
propeller will turn but the larger the propeller we can turn. So you can
use a gearbox to help provide more thrust so you can fly larger planes with
a given motor. However you will be turning the propeller slower so the
plane will not go as fast with the same propeller.

With direct drive, that is when the propeller is directly attached to the
motor shaft, we are running in high gear ( no gear reduction). Like pulling
your car away from the light in high gear. Assuming the motor doesn't stall,
acceleration will be slow, but over time you will hit a high top end!
Typically direct drive propellers on a given motor will have a smaller
diameter.

With the geared motor, it would be like pulling away from the green light in
first gear - tons of low end power and lots of acceleration, but your top
speed is reduced.

So, by matching up the right gear ratios made up of the propeller and,
optionally, a gearbox we can adjust the kind of performance we can get out
of a given battery/motor combination. How this is done is beyond the scope
of this article.

At one time gearboxes were more common. However the use of "outrunner"
brushless motors has become the standard for small to medium sized planes.
Gearboxes are still see a lot in gliders, where they can help fit a motor into a
very thin nose, or in very large aircraft where a suitable outrunner type
motor may not be available.

NOW WE CAN START TO MATCH
UP THE PIECES!

The simplest approach I have seen to figuring power systems in electrics is
input watts per pound of "all up" airplane weight. The following guidelines
were developed before brushless motors were common but it seems to hold
pretty well so we will use it regardless of what kind of motor is being
used. You may see variations on these numbers but the concept is the same.

50 watts per pound = Casual/scale flying

75 watts per pound = Sport flying and mild aerobatics

100 watts per pound = Sport aerobatics -
This is a good target for pilots who are used to glow powered planes

150+ watts per pound = Aggressive aerobatics, pattern, 3D.

Remember that Watts = Volts X Amps. This is a power measurement.

In case you were wondering, 746 watts equals 1 horsepower.

AN EXAMPLE!

This should be fun. Let's see where these formulas take us! We will use a
24 ounce, 1.5 pound plane as our example. If we want basic flight you will
need 50 watts per pound or about 75 watts input to your motor for this 1.5
pound plane. That is, 50 watts per pound X 1.5 pounds = 75 watts needed
for basic flying performance. If you want a little more spirited plane, we
could use 75 watts X 1.5 pounds which is about 112.5 watts.

Lets use 100 watts as the total target, just to be simple, shall we? I am
going to use a lot of round numbers here. I hope you can follow.

The Battery:

If we use an 8 cell NiMh battery pack at 9.6 V it will have to deliver 10.4
amps to hit our 100 watts input target ( 100 watts/9.6 V = 10.41amps) If
my battery pack cells are NiMh cells that are rated at 10C then I need an 8
cell pack rated at 1100 mah to be able to deliver 11 amps. Sounds about
right.

Now I select a motor that can handle 100 watts or about 10.4 amps at 9.6
Volts. From experience we know this could be a speed 400, a speed 480 or
some kind of a brushless motor.

We now need a propeller that will cause the motor to draw about 100 watts. I
don't know off the top of my head what that would be. I would go to some mfg
chart as a starting point. GWS has good charts!

I see that if I use a direct drive speed 400 with a 5X4.3 prop at 9.6V then
the motor will draw about 12.4 amps or about 119 watts. This would be a
good candidate motor/prop for the plane using a 9.6V pack that can put out
12.4 or more amps. This would be a set-up for a fast plane as that motor
will spin that small prop very fast.

However maybe I don't want such a fast plane but one with a really good
climb and lots of low end pull to help out a new pilot who is in training or
to do more low speed aerobatics

I can also use a speed 400 with a 2.38 gearbox and run it at 9.6V spinning a
9X7 prop and run at about 12.8 amps for 120 watts.

The larger prop will give this plane a strong climb, but since the prop
speed has been reduced by 2.38 times, it won't be as fast. Spinning a
bigger prop gives me more thrust. Also note went from a pitch of 4.3 on the
direct drive set-up to a pitch of 7 with the gearbox. This is because the
prop is turning 2.38 times slower now so we increase the pitch to somewhat
balance that.

Back to battery packs and motors

So if I shop for a 9.6V pack to be able to handle about 15-20 amps, I should
do just fine and not over stress the batteries. In NiMh that would probably
be a 2/3 or 4/5 A pack of about 1500 -1600 mah capacity.

We view the battery and motor as a linked unit with a target power profile,
in this case about 100 watts. We use the prop and gearbox, if any, to
adjust the manner in which we want to deliver that power to the air to
pull/push the plane.

If this is a pusher, I may not have clearance to spin that big prop so we
may have to go for the smaller but faster prop combo.

If this is a puller, then we can choose our prop with more flexibility but
we may have to limit it by ground clearance or some other criteria.

See, that was easy, right? ( well sorta but ....)

But we are not done! Oh no!

I could try to do it with a 2 cell lithium pack rated 7.4V. To get 100 watts
I now need a pack that can deliver 13.5 amps and a motor/prop combination
that will draw that much. So if I have 10 C rated lithiums, then the pack
better be at least 1350 mah. Probably use a 1500 mah pack to be safe.

Well, when I look at the chart for the geared speed 400 I see that,
regardless of prop, at 7.4V I am not going to have enough voltage (
pressure) to draw 13 amps based on the propellers they tried. So the

We see that the best I can get this speed 400 to do is a total of 70 watts
at 7.2V ( close enough ) so I can't hit my power goals using a speed 400 at
this voltage. but 70 watts would be about 48 watts per pound so I could have
a flyable plane, but not an aerobatic plane using this two cell pack.

REALITY CHECK!

Now, in fact that is NOT how I would do this. I would decide on the watts
per pound target that would give me the type of performance I want.
I would then go to a chart, find a combo that meets my goals, then select a
battery that will meet the demand and see if my weight comes up at the
target I set. A little tuning and I come up with a workable combo.

I often use the MaxxProd combos for reference. If you read the details on
each package they have wonderful information. And, the fact is that I
generally go with brushless motors these days. Costs are reasonable and
their higher efficiency gives me more performance and longer flight times.http://www.maxxprod.com/mpi/mpi-264.html

Following the example above, the combo 10 on that page would be an excellent
fit for my 1.5 pound plane for sport flying. The Combo 049 might be a good
fit for a slow flyer. Either way the package has all I need.

If I wanted the plane to have all out performance, the 15A or 19A package
would be my pick. Note that these would need either higher voltage or
higher amperage battery packs. The flyers/PDF for the packages make
recommendations.

For those who like to be even more analytical about it, there are packages
like MotoCalc that will allow me to play with all sorts of combinations and
make suggestions on what I should use. There is a link for MotoCalc below.

SUMMARY

So, in these few paragraphs you have taken in a basic knowledge of how
electric power systems are sized, the factors that are considered an how to
predict the outcome.

Simple, right?

Of course there is a lot more to know and time and experience will teach
you plenty, but with this basic understanding you are better prepared to
begin playing with the power systems you put in your planes.

A commercial tool that will tell you everything you need to know: Amps,
Volts, Watts, RPM, Thrust, Rate of Climb, and much more! It is a popular
tool for predicting the proper motor, prop, battery pack for electric
planes. There is a fee but if you are going to do a lot of this kind of
work, it may be a good investment.

Your electric motor draws a certain amount of energy to do its job, which is to turn the propeller. With no prop attached it draws very little energy. If you put a big prop on the motor it draws a lot of energy.

This is similar to pulling a boat trailer behind your car. The car might get 20 mpg normally, but put a boat on a trailer behind the car and mileage will drop off to perhaps 15 mpg because the motor is using more energy just to maintain the same speed and travel the same distance. However as long as the boat and trailer are not too heavy, no real damage occurs, you just use more gas.

If you put too big a trailer behind your car, something will break. The motor may fail, the transmission may fail or something else. That is because you are asking the drive train to produce more work, use more energy then it was built to handle. Fuel mileage goes way down and then something breaks. You have over stressed things.

Back to your plane.

Your electric motor needs to "draw" a certain amount of energy in order to turn a given propeller at a given speed. Let's use a speed 400 motor as an example and let's say you have a 6X5 prop on it. That means the propeller is 6" across and has a pitch of 5" per revolution. Pitch indicates how far the prop would move forward through the air if there was no slippage. As either of these numbers go up, the motor is asked to do more work.

Now let's apply some numbers. These are made up numbers for illustration only. Don't assume that these are accurate for your motor in your plane turning your prop.

Let's say that, to turn that 6X5 prop your speed 400 motor draws 6 amps of electricity using a battery that delivers 10 volts, just to make the math simple. That would be 60 watts of energy that the motor consumes to turn that prop. (6 amps X 10 Volts)

If we go to a larger prop, say 7 inches and keep the pitch the same 5 inches, the draw might go up to 8 amps at 10 volts or 80 watts.

Likewise if we went to a 7X6 prop, the draw would go up again, say to 9 amps or 90 watts.

In each case we are increasing the amount of work the motor has to do to turn the prop. The harder it works the more electricity it draws. This is also placing an increasing amount of stress on the motor causing it to generate heat and placing more pressure on the bearings. If we push it too far, the motor will be unable to turn the prop fast enough to be useful in flying the plane and/or it will fail from stress, just like the car example above with the trailer that is too big.

What we are try to do is to get the best balance of propeller and amp draw so that the motor operates efficiently without being over stressed.

Likewise if you have that same speed 400 motor and keep the prop at 6X5 but increase the electric pressure, volts, to 12 volts it will try to spin the motor faster causing it to draw more amps into the motor. This would be like putting a supercharger on your car's motor which forces more fuel/air mix into the car's engine. It will produce more power so it can do more work. However if we exceed the amount of power it was designed to handle, it will fail. It might not fail right away, but over a very short time it will start to degrade, perform badly and perhaps suddenly fail all together.

If we push the voltage up too high or the amp draw too high, we will over stress the motor and damage it.

MotoCalc
MotoCalc will tell you everything you need to know: Amps, Volts, Watts, RPM, Thrust, Rate of Climb, and much more! It is a popular tool for predicting the proper motor, prop, battery pack for electric planes.http://www.motocalc.com/

Understanding the Electronic Speed Control
Amended 11-2008
By Ed Anderson

When we look at model airplanes that have electric motors as opposed to liquid fuels, the things we notice first are the quiet electric motor and the battery. However there is a component that sits between them called the electronic speed control that is really the master control point for all power in the plane. We are going to look at its make-up and how it does its job.

On the surface we can see that the electronic speed control, the ESC, takes over the function of the throttle servo that would operate the carburetor in a glow or gas powerd plane. Just as the throttle servo controls the speed of these wet fuel motors, the ESC controls the speed of the electric motor. But there is more to it than that.

The first thing that we want to recognize is that there are two different kinds of ESCs that are specific to the type of motor they control. There are brushed motors, such as the speed series or the Mabuchi motors, and then there are the brushless motors. Each type of motor needs a different electronic speed control.

Understanding the Wires

When you look at an electronic speed control, you notice that you have three sets of wires. Typically two sets of thick wires and one set that looks like a servo wire.

Two of the thick wires, typically black and red, connect to the battery. The ESC will usually be marked to tell you which are the battery wires. They would connect to the battery as red to red and black to black.

A second set of wires, typically thinner than the battery connection wires, has a plug on the end that looks like a servo plug. This will be connected to the receiver and will serve two purposes as it sends power to the receiver and gets signals from the receiver.

If we look at the wires on this plug they usually run from a dark or black wire on one side to a light or white wire on the other side. I am going to use black, red and white for this discussion. Yours may be dark brown, orange, yellow or something similar.

The black and red wires feed power to the receiver which in turn distributes power out to the servos and other accessories that are plugged into the receiver. Note that the red wire is in the center. This is the power wire. Since it is in the center you can insert the plug into the receiver either way and nothing bad will happen. You won’t get any response from the servos if you put it in wrong, but you won’t damage anything. Note that, on some older systems, particularly Airtronics radio systems, the red wire was on the end. If you plugged it in the wrong way it could damage the receiver and possibly the servos. However the center red design has been fairly universal for many years.

The third wire, the white wire is the signal wire that sends commands from the receiver to the ESC to tell it how to control the motor. As you move the throttle control on your transmitter, the receiver gets the command and passes it up the white wire to the ESC so it knows how much speed you want from the motor.

There is a third set of wires that go to the motor. The ESC is usually marked to show which wires are the motor wires. If this is a brushed motor ESC then there will be two wires, typically red and black.

On a brushed motor ESC, if we connect red to red on the motor, and black to black, the motor will turn in the expected direction. If we reverse them the motor will spin in the opposite direction.

On a brushless ESC, you will have three wires going to the motor. If there are colors, you can match color to color as well. However if the colors don’t match don't worry. Connect them up and observe the direction of the motor. If it is spinning in the wrong direction, reversing any two wires will correct this.

Note that on some older brushless motors there were additional wires that attached to a sensor in the motor. However, unless you have an old motor and ESC combination you won’t see that on any of the current designs.

Some ESCs have an integrated switch. In most cases this will allow or prevent the motor from running and pass or block power to the receiver. However it typically does not stop the flow of current from the battery to the ESC. In fact, even if there is no switch there is always current flowing to the ESC which will drain the battery.

It is for this reason that you should never leave your battery connected when you store your plane. This small current drain will take your battery to zero charge over time. If you are using NiCd or NiMh, the damage may be minor. If you are using Lithium batteries, you lithium battery pack will likely be ruined. So, don’t leave your battery connected unless you are preparing to fly.

Connectors

The connector/plug that goes to the receiver is standardized. It is the same wire scheme and plug type as is used for the servos. Today all makers, except Futaba, use the universal plug.

On the Futaba J plug you have the same wiring scheme but there is an extra tab on the plug that insures the connector is inserted properly into the receiver. If you have a receiver that accepts this slotted plug it will also accept universal plugs. However if you have a receiver that expects the universal plug, then you will need to trim off this tab with a hobby knife or you can sand it off. Once trimmed, the plug will work fine.

Battery and motor connectors are not as simple.

There is an emerging standard for motor/ESC connection on brushless motors. The connectors are round and are called bullet connectors. Most brushless motor/ESC makers seem to be using these now, so on brushless motors this connector standard seems to be established. However, for brushed motor connections there is no standard.

On the motor side we have the option of not using a connector as we can solder the motor and ESC wires together. This works fine if you don’t plan to remove the motor or the ESC and it gives the best connection. However if you do have to remove one of them for service, you will need the soldering iron in order to take the connection apart.

On the battery side we always use a connector so that we can remove the battery for charging and storage. When flying electric planes it is common to have several battery packs so the connector allows us to remove one pack and insert a fresh one while the first is charging.

Whatever batter or motor connector you use, make sure that is has a current, amp, rating that is larger than what the motor is likely to pull. The reason the wires for these links are thicker is that the battery has to deliver high current to the motor as opposed to the relatively small current that goes to the receiver. If the connector can’t handle the flow, it will heat up and potentially be damaged. Likewise, if the connector can’t handle the current the motor will never develop full power. Too light a connector can also cause a serious voltage drop.

This lack of standards leads to situations where you buy a motor that has one connector, your battery has a different connector and your ESC has a third type. Or, as seems to becoming more common, none of them have connectors and you have to add your own.

My suggestion is to standardize connectors. Once standardized, any motor or battery connection that doesn’t have your standard connector gets a connector replacement. It takes time and soldering but with one standard, all of your batteries will work in any plane for which they are appropriate and you can move motors and ESC around as you desire.

This will also simplify your battery to charger connections. One or two adapters for your charger will handle all of your batteries. Just make sure the connector you use can handle the current.

I have three standards. For brushlesss motors, I use the bullet connectors. For small brushed motors and batteries in very small light planes where the current will typically be under 5 amps, I use the red BEC connectors. These are sometimes called GWS connectors as they are common on GWS motors, batteries and ESC. They are small and light and are well suited for small light planes.

For my high current applications I use the Deans Ultra connectors. They can handle high currents, are easy to solder and can be easily removed and reused. However there are many other high current connector that are equally as good. As long as it can handle the current flow, it will be fine.

Sizing an ESC

Electronic Speed Controls are sized according to how many amps they can control and the voltage that they can handle. So you may see an ESC marked as 20 amps and 7-10 NiXXcells or 2-3 cell Lipo. That says it can handle a 20 amp flow using a battery pack that ranges between 7.4V and 12 volts. If you use it with a motor/battery system that is outside this range it will likely fail. When it fails it may simply not run the motor or it may also cut power to the receiver, which will lead to a crash.

You size your ESC according to the motor and the battery you are using. I won’t go into how we determine what the motor and battery will need. That is covered in another article. It is enough to say that, if your motor is going to draw 20 amps you will need an ESC that is rated for at least 20 amps. There is no problem having an ESC that is rated for more amps than you need, but and ESC that is rated below the expected current load will likely lead to a failed ESC.

The same goes for the voltage. Use your ESC outside the voltage it is designed for and you can expect it to fail.

Your ESC will likely have an integrated battery elimination circuit, a BEC. This is the part that delivers the power to the receiver. Always check the specs for the BEC. While the ESC might be able to handle 14.4 volts, the instructions may say that for uses above 11.1V you may have to disable the BEC. There is a complete article on the BEC, so I won’t go into it here. Let’s just say you need to check this.

I recommend that you always have at least a 20% margin between the amp requirements of your motor and the rating of your ESC. This way you will know you will not be overloading the ESC. A bigger margin is also fine.

How the ESC controls the Motor

Motors are rated by Kv, which means the number of revelations the motor will turn when you apply 1 volt of electricity. So a 1200 Kv motor will spin at 12,000 rpm if you apply 10 volts.

From this you might imply that the ESC changes the voltage to the motor in order to change the speed of the motor, but that is not the case. If you look at the specifications for your ESC you will probably see a frequency number. This might range from 2 KHz to 12 KHz or higher. This is related to how fast the ESC can pulse power to the motor. You see your ESC is not a variable resistor that adjusts the voltage to the motor, it is a fast switch that pulses power to the motor.

You can think of this as a duty cycle control. How long will the ESC leave the power on till it turns it off? Then, how long will it be off before it turns it back on? There is no need for you to know this cycle time, only that on every on cycle your motor is getting the full voltage of your battery.

I take the time to explain this because people mistakenly believe that if they run their motor at partial throttle they are sending reduced voltage to the motor. If the motor is not supposed to get more than 7.4 volts and you put in an 11.1V battery, running the motor at ˝ throttle does not reduce the voltage to the motor. It is getting 11.1V hits every time the ESC switches on. On a brushed motor that is receiving too much voltage, this will typically produce arcing which will burn up the brushes on the motor. In addition to this arcing on brushed motors, this higher electric pressure may push too much current that will overheat the motor.

If you have had a motor “burn up” even thought you usually ran it at a partial throttle setting, this may be the reason. Understanding how the ESC controls your motor will help you diagnose problems.

Note also that, since the ESC is switching power on and off it is also producing electromagnetic pulses, or radio waves. The electronics in the ESC will typically be designed to reduce or shield some of this radio wave noise, but it can’t block it all. This is why we recommend keeping the ESC and the receiver as far apart as possible as this ESC noise can interfere with the receiver. If you are getting “glitching” or odd pulses to your servos, these may be coming from ESC noise bothering the receiver. Try moving things around.

Other Components in the ESC

I am going to address these in later articles, but there are typically two other components that are integrated into your ESC. We already mentioned the BEC. The other is the LVC, the low voltage cutoff. These are not directly involved in controlling the speed of your motor, but as you will see in the articles that are focused on these that they are very valuable parts of your ESC that you will want to understand.

Summary

The electronic speed control is the power system controller for your airplane. Its various components distribute power to the receiver and control the speed of the motor. Understanding how it works will give you the ability to properly size and install the ESC and to diagnose problems in the system.

=========================MY MOTOR WON'T RUN - WHAT'S WRONG?
A tip for new electric pilots - Setting the throttle to zero

Before most Electronic Speed Controls, ESC, will allow the motor to run they require that you move the stick to zero throttle. This is a safety feature that prevents the motor from coming on the moment you connect the battery.

But, is your throttle stick it really at zero?

There is a trim on the throttle channel, just like the other channels. On glow planes they use this to set the idle, so the motor won't shut off when they go to zero throttle position. In other words the throttle isn't really at zero.

But we don't have to worry about idle on electric models. So we want the throttle to be able to go to zero.

If your throttle trim is set to the center, then your throttle channel may not really be going to zero. This can result in your ESC not arming and not allowing your motor to run. If this happens to you, move that trim on the throttle channel till it is all the way down, to zero. Now connect the battery and see if the ESC will arm and the motor will run.

This came up because a friend with a new electric plane had this problem. When he called for support, they thought it was a defective ESC and sent him a new one. But that one did not work either. So he called me. Well, I have been down this path before, so after trying a few other things, we moved the trim all the way down.

The Low Voltage Cutoff Feature of your ESC
By Ed Anderson
aeajr on the forums

Many electronic speed controls include a feature called the low voltage cutoff
circuit, the LVC. The LVC watches the voltage that is being delivered by the
battery. When it gets below a certain level, it will cut power to the motor to
preserve power for the radio system. This will allow you to keep control of the
plane and land it in a glide.

Power draw by your receiver and servos is a tiny fraction of what the typical
electric motor draws. As the battery drains it will exhibit a voltage drop. You
may feel this in the way the plane flies. The plane may become sluggish or it
may not be able to climb under full power. This is a clear indication that the
pack is getting low.

A battery that can't sustain voltage when the motor is on, can still provide
plenty of power for the flight electronics and may be able to do so for quite a
while, but don't test it. If your motor cuts, enjoy the glide, but set up to
land as soon as possible. I always teach new pilots how to glide their planes
so, if the LVC cuts the motor, they don't panic.

If you practice flying your plane with the motor off, then an LVC cut will be no
big deal. You might even find you enjoy gliding, which can extend your flying
time. I often glide and thermal my electric planes just for fun.

LITHIUM BATTERIES CHANGE THE ROLE OF THE LVC

If you drain NiCd or NiMh packs too low, usually there is little damage. Just
bring them back to charge a little slower than normal. If you drain a lithium
cell below 2.5V resting voltage, typically the cell will be damaged. So, in
this case the LVC is protecting your plane and your battery packs.

Most lithium friendly ESC will cut the motor off if the pack voltage drops below
2.7 to 3.0V per cell under load. At this level there is very little useful
charge left in the pack and the voltage will continue to drop fast.

Note that when you cut the load of the motor the voltage will likely pop back to
3.1, 3.2 or even 3.3 V per cell. If you check your batteries after you land,
you may think that LVC has malfunctioned, but it has not. The battery may be
3.3 V/cell resting but it can't sustain it with the motor running.

One thing you might want to be aware of is that the voltage sag will be less at
lower throttle settings. If the LVC cuts the power at a particularly bad time,
you may be able to get a short burst of motor operation at a reduced throttle
setting. A short run at half or quarter throttle may be all you need to get you
over that fence, past that tree or properly aligned with runway. But don't push
it by trying to extend your flight with lots of short bursts. However if it
will help you avoid a crash, or two short runs, to save the plane, are worth the
risk to the battery pack.

CONCLUSION

The LVC was put there to protect the radio, but if you are using Lithium
batteries the LVC can protect them too. It is best to be sure your ESC/LVC is
lithium friendly. That means either that it can be set manually, or that it
senses how many lithium cells you have and sets automatically. Even if it is
not designed for Lithium cells, if you can set the cut-off at something above
2.75V per lithium cell, then you should be OK.

I thought it would be a good investment as I was doing more in the area of
mixing and matching motors, props, and the like. It is small and simple to
use so I put it in my field box. It wasn't long before it started to show
its value.

We were flying one afternoon when one of the club members felt he was not
getting
good performance from a new plane he had built. I put he wattmeter on the
plane and determined he was pulling about 9 amps. Turned out the pack he
was using really was not up to the load and the voltage was dropping off
excessively. As a result he was not getting the RPM out of the prop that he
expected. Problem discovered and cause identified in a few seconds. He
needed stronger battery packs.

A few weeks later we did the same thing with another plane. There was a
concern that the LiPo being used might be getting over worked. However the
Wattmeter showed that it was working well within its rated capacity. Flying
went on with confidence.

I recently purchased an Easy Glider Electric from another club member. He
had upgraded the motor from the stock speed 400 to a brushless, a 27 amp ESC
and was using 2 cell 2100 MAh LIPOs. I bought the whole package.

The plane flies very nicely on the 2 cell packs, but I had a 3 cell pack
that I thought I might add to the rotation and REALLY boost the power. The
ESC could handle 3 cell LiPo so I did not see a problem. I assumed the
system was probably running at about 18 amps which was within the rating of
this pack. Should be a good fit.

Fortunately before I tried it in the plane I put the watt meter on the
system. I was surprised to see that the system was running at 26 amps on
the 2 cell lipo packs. That was much higher than I had expected. It turned
out that the 2 cell packs were an excellent match for the motor and speed
control. The amp load was well within the specs of the 2 cell packs being
used and the plane flew very nicely on this combo.

If I had blindly put a 3 cell pack in there I would have pushed well past
the ESC's 27 amp rating and probably burned out the speed controller. Or,
in the case of my 3 cell pack, it would probably have pushed over 30 amps
into the system due to the higher voltage, but it was not rated for that
high of an amperage and would probably have had a short life working at that
level. I would have thought it was just a crummy battery pack but in fact I
would have been over working it.

Operating in the blind I would have ruined the ESC, or the pack, or both. A
very expensive mistake. Certainly more than the cost of the watt meter. It
had just paid for itself.

A few days ago I pulled out my old Electrajet to prepare to sell it. I had
purchased it almost 3 years ago, but had never really been happy with the
plane and my interests have turned more toward gliders and slow flyers
rather than a pusher jet. When I purchased it I also bought some cells and
made up some 8 cell packs. However it really didn't seem to have the zip I
thought it should. I just attributed it to the speed 400 motor and the
plane being too heavy.

I put the watt meter on the motor/battery combo. The motor sounded about as
I had recalled. When I checked the meter, low and behold, those 8 cell
packs were duds! They were 9.6V 8 cell 1000 MAh packs rated for 10C. At
rest, fresh off the charger they were reading 11 volts, but when I hooked
them up they were both dropping to 7 volts while delivering 9 amps. That is
way too much drop! The problem was not the plane or the weight of the plane
but the quality of the cells I had used.

I tried one of my 15C Lipo packs and that held voltage well, delivering 13
amps. The motor screamed! Now that was more like what I had expected.
Hummm, maybe I won't sell it after all. I just need to put better battery
packs in it.

I also tried a 1000 MAh 2 cell lithium pack that is rated at 10 C. The
voltage sagged to 6.6 volts almost immediately. The motor ran but I was
clearly over stressing the pack. This pack would have been ruined in very
few flights if I had used it to fly the plane regularly.

I share this story only to help you understand that, without a watt meter,
or the use of a multi meter with knowledge and skill, we are working in the
blind. We really don't know what is happening in our power systems.

WHO NEEDS A WATT METER?

While the watt meter is a nice to have, some people don't need one. If you
are buying RTF planes, or ARF or kit planes and are using the manufacturer's
supplied motor and battery packs, I would say you can be pretty confident
that all is well.

However, if you start mixing and matching motors, gear boxes, props,
controllers, battery packs and the like, you are really working in the blind
if you are not measuring the energy flow in the system. In my case, I
started making my own battery packs but I was not measuring their
performance. Now I know the true results.

There are a variety of watt meters out there. This one is easy to use and
fits nicely in my field box, but there are other good ones.

If you are going to upgrade your power systems or make up your own packs, you need a
watt meter. You can perform many of the same tests with a millimeter if you
know how to work with shunts and the like, but if you want a simple to use
tool that does exactly what you need it to do, this is hard to beat. It has
other uses too, so read the instructions, but for this use alone it paid for
itself pretty quickly.

At the time this was originally written, 2005, most electric planes were
using some kind of brushed motor as brushless motors were still very
expensive. As of today, brushed motors are seen mostly in micro models
and brushless motors are the standard. However the article still has value
for those using brushed motors or applications where a brushless
in-runner matched with a gearbox would be a good choice. This is often seen in
sailplane.

We can also look at brushless inrunners as being similar to brushed motors in
that they are typically high kV, high revving motors. In helicopters they are
usually matched up to gearboxes. In airplanes they likewise are often matched up
with gearboxes. So I will leave the article here with your understanding that the
purpose and use of a gearbox remains the same. And in some applications the use of
a gearbox is quite common such as helicopters and sailplanes.

==========================================

We are going to discuss why we would consider adding a gearbox to a brushed
electric motor or a brushless inrunner motor.

I am going to get real loose with the words "gear ratio" for a moment, but try
to follow me. Think of gear and gear ratio as the way we adjust the load on the
motor. I can adjust the "gear ratio" on my motor/propeller set-up in one of two
ways:

1) change the propeller
2) add a gear box and change the propeller

The goal is to get the motor spinning, at full power, at its optimum watt range
so that we do not over burden it, but so that we get the power to the propeller
efficiently. We are trying to get the best balance between pitch speed, thrust
and current draw.

If I increase the diameter of the propeller while holding the pitch constant I
put a greater load on the motor. A 10X6 prop puts a greater load on the motor
than a 9X6 prop. It will cause the motor to draw more power, more amps. At the
same time, it may load it enough that it causes it to slow down. Its peak RPM
may will be less. This is similar to changing gear ratios on your bicycle.
You can feel the effect in your legs.

If I deepen the pitch on the propeller while holding the diameter constant, I
also increase the load on the motor. A 9X6 going to a 9X7 going to a 9X8. In
this case I am increasing the "pitch speed". Again, this is similar to changing
the gear ratio. As I go to a deeper pitch the current draw will increase, the
watts increase and we may again load the motor enough to decrease its top rpms.

If I go too wide, or too deep, I can overload the motor and burn it out.

So, on a direct drive set-up, no gearbox, I tune my propeller between pitch and
diameter to get the motor to the power range I want. Again, this is EXACTLY the
same as changing gear ratios, in practical application.

To some extent I can trade pitch for diameter and vice versa. So you will see
motors listed as accepting a range of propellers. Typically as diameter goes
up, pitch goes down.

9X7
10X6
11X5

For this sample motor, each of these props will probably produce a similar watt
output but they do it with different results.

The wider prop will provide more thrust but the lower pitch will produce less
speed. So I can tune for the application. Sailplanes typically want more
thrust for steeper climb but are not as concerned about speed. Pylon racers
are less concerned about climb or acceleration as they are about top speed.
Hopefully you get the idea. I am tuning the "gear ratio" by changing the prop.

If you are not with me up till now, then ask because what comes next depends on
your understanding what is above.

ADD A GEARBOX

Now, suppose I have a given motor, say a brushed 550, and my prop choices don't
give me the thrust I want to take my 2 meter sailplane up at a steep enough
angle to make me happy. It takes too long to get to soaring height. Or,
suppose I want to fly a larger, heavier plane with the motor I have. My prop
choices don't give me enough thrust to handle the heavier plane. What do I do?

I can put in a gear box. The gearbox will have two effects. It will reduce the
top speed to the prop, but it will increase the torque available to turn the
propeller. This allows me to go to a wider propeller but my top speed will be
reduced. Now I can get an steeper climb, or perhaps I can fly a larger or heavier
plane. I am going to stay with the sailplane for the rest of the discussion, but it
applies equally to any kind of aircraft. We are talking gear ratios.

Again, using the bicycle example, you shift to a lower gear to go up the hill.
You can get up the hill in first but if you were to go to third you might not have
enough power in your legs to turn the pedals. So you tune the gear ratio to
match the available power.

A typical prop on a 550 motor in a sailplane, like a Goldberg Electra would be
an 8X4 prop. That is the widest prop, the highest thrust prop that this motor
can comfortably turn and provide enough speed to fly the glider. The motor will
likely pull about 18 amps on an 8.4V pack. It will fly the plane but the climb
angle might only be about 25 degrees. So it might take me 2 minutes to fly up the
height I want to reach. This plane isn't really made for speed, so going to a
7X6 prop, trying to get more speed, won't help.

But if I put a gear box on, say a 3:1 ratio, I can go to an 11X8 or a 12X7 prop.
Now I get a lot more thrust and the plane will climb at a 50 degree angle. Now
I get to height in less than a minute and the motor might only be pulling 16
amps. I climb in less time AND I may be drawing fewer watts to do it.

That is why we go to a gear box. Usually it is to allow us to swing a wider
prop at a slower speed in order to get more thrust at the sacrifice of speed.

WHAT ABOUT BRUSHLESS INRUNNER VS OUTRUNNER?

Because we have two motor types in the brushless world we add flexibility and
complexity. More choices means more to decide.

The gearbox discussion with a brushless inrunner is exactly the same as for the
brushed motor above, so I won't repeat it.

However if we look at outrunners vs. inrunners we see that outrunners tend to
spin slower/volt with more torque. This has a similar effect to having a
gearbox on an inrunner. So how do you decide?

Some people don't like gearboxes. It is another thing to maintain and another
thing to break. Also gearboxes tend to make noise and some people don't like
that. However there is nothing spinning around inside the plane with a gearbox.
So you can mount the motor/gearbox without regard to clearance as long as you
have adequate air flow. You can just clamp a gearbox/inrunner to the frame of
the plane and you are done. I have seen motor/gearboxes left loose in the nose
of the plane. The Multiplex Easy Glider is set-up this way. No mount at all,
it just sits there.

Outrunners need space. You have a spinning can that must be protected from
contacting another surface, lose parts, wires, etc. Grass, string, stuff can
get caught on that spinning can. In some cases this could be a problem, so a
gearbox might be preferred.

I have read that brushless inrunners are typically more efficient than
outrunners. Even with the gearbox losses I have read that inrunners are still
more efficient at turning those bigger props. So, if that is true, and if that
matters, it could shape your decisions.

Summary

We can tune our power system by adjusting the "gear ratio". This can be done by
changing props to some degree. After that we go to gearbox systems to tune our
power systems to give us the performance we want.

EXTENDING FLIGHT TIMES WHILE MAINTAINING BALANCE
by Ed Anderson
aeajr on the forums

Changing the type or capacity of your battery pack is typically done for one
of three reasons:

* You want longer flights
* You want to reduce weight.
* You want to do both

Here are some points to consider to get the most out of this change.

If you are currently flying NiCd packs, you can go to NiMh very easily. You
will gain about 40% in battery capacity at the same weight. The packs are
about the same size and shape so they fit easily and should not throw off
the plane's balance. NiMh and NiCd packs, NiXX for short, therefore can
typically be interchanged easily. I have eliminated virtually all my NiCd
motor packs and replaced them with NiMh packs.

If you go to lithium batteries you can either make your plane lighter or you
can maintain its weight but double, tripple or quadruple your battery
capacity. Lithium batteries have about 4 times the capacity per ounce as
compared to NiCd packs. Here are some steps to consider BEFORE you buy the
new pack:

Where is you battery pack located?

If your battery is forward of the CG, the balance point, then its weight is
helping to balance the plane. If you go to a pack of a different weight,
you MUST rebalance the plane or it won't fly well. For example, a lighter
pack will shift the CG toward the rear which may make the plane difficult or
impossible to fly. You must keep the plane in balance so that the CG,
center of gravity, the balance point, is in the right place.

This also applies to going to heavier packs as they will shift the CG
forward. A slight shift forward might not be a problem if you are adding
voltage as the more powerful pack will drive the motor faster which may mask
a slight change in balance and a more forward CG can make the plane more
stable. For Example I shift between 6 and 7 cell NiMh packs in my Aerobird.
The CG moves a little forward with the 7 cell pack but not enough to
seriously effect the way the plane handles. But optimally you want to keep
the CG in the same, the best location.

From here on I am going to assume you are going from NiXX packs to lithium
packs, as this is what many are doing and the one that takes the most
planning.

Before you buy that new pack:

* Weigh your current battery pack. A food scale or a postal scale is fine.
Many post offices in the US have self service scales. Great for weighing
stuff. Get it to the nearest .1 ounces. Write it on the pack so you won't
forget it.

* Now look at the space in the plane. Can the new pack go in the same or
almost the same place as your current pack? You can account for a location
shift by changing the amount of weight you add to the new pack.

Now decide on your goals based on what you can do in this plane and how much
money you want to spend.

1) Keep the weight the same and spend more money - Get a pack that fits in
the current space and weighs the same as your current pack - Now you can use
the new pack and your current packs interchangeably. Good deal! However
lithium packs are different sizes and shapes than NiXX packs so this might
be hard to do. If it is close, you might be able to modify the battery
space to allow the new pack to fit. A 600 MAh NiCd Pack weighs about the
same as a 2000 to 2400 MAh Lipoly pack, but the LiPoly may cost more.
Prices are dropping all the time and 4 times the flight time is definitely
cool!

2) Keep the weight the same and spend a bit less - Get a pack that is
lighter than your current pack and will fit in the same or close to the same
location, perhaps with minor mods to the plane. Maybe you go from a 600 MAh
NiXX pack to a 1300 MAh lithium pack rather than a 2400 MAh pack. This will
probably have a better chance of fitting where your NiXX pack fits. Great!
Add weight to the pack so it weighs the same as your NiXX pack. You can
still use both without serious modification to the plane. Good deal!

3) Make the plane lighter - If you can move stuff forward in your plane so t
hat a lighter battery can balance the plane, you can avoid the need to add
weight. Now you have a higher capacity battery pack AND your plane is
lighter. Lighter planes generally fly better. The only problem with this
approach is that your current "heavy packs" may not be able to be used
anymore unless you can leave space to adjust their position rearward.

If it won't fit, can you modify the space to make it fit?

If you remove foam, consider reinforcing the space with tape or glue and
light plywood as you have removed some of the structure of the plane. Can
you cut a hole in a former so the pack fits under it? Make sure you
reinforce to account for any cut away structure. By the way, tape, glue,
bals or plywood add weight so you so take these into account. Cut a little,
set some reinforcing in place but don't glue it. Position the pack and test
the balance of the plane; adjust accordingly. Be sure you pad the pack in
balsa or plastic planes so that a crash will not likely damage the pack.
Lithiums can not take the physical abuse that the NiXX packs tolerate.

If modifying the plane to move the pack forward won't get it done, then see
if you can move other things in the plane to shift their weight forward.
Some people have the receiver under the wings. Move it forward and it will
help to balance the plane and you won't have to add as much weight to the
lithium pack. Also see if you can move the ESC forward. Move any excess
wire that you have bundled to the forward area. Wire has weight.

If you have any components, like the receiver that sit behind the CG, moving
them forward will make a huge difference.

If you can move your electronics forward enough that you can balance the
plane without the battery pack, then you can set the battery directly over
the CG. Now it doesn't matter which battery pack you use as the weight of
the pack will not shift the balance of the plane. You can interchange packs
all you like.

When I rebuilt one of my sailplanes after a crash, I positioned my servos,
receiver and battery to more forward locations than the stock
recommendation. As a result I made the plane about 12% lighter with no
other modifications. That made a HUGE difference in how if flew.

I then made a removable motor for it and positioned it on a pod that sat
right over the CG so I could put it on or take it off without changing the
balance of the plane. Likewise I placed the battery right over the CG.
With the motor and battery mounted, the plane was much heavier, but it
stayed in perfect balance whether they were on or off the plane.

There are other considerations related to lithium batteries. You need a
special charger and charging procedures. You MUST protect them from damage
as they can not take the same abuse as NIXX packs. But these are covered in
other threads. This one is just about maintaining balance.

Clear Skies and Safe Flying!

* See if you can buy a lithium pack that is the same weight as your current
battery pack. If you can, and you can afford it you are all set and have
two to four times the flight capacity for longer flights.

All RC planes use battery packs to operate their electronics. On planes
that don't have electric motors we call these receiver packs as they power
the receiver and the receiver then distributes the power to the servos and
other electronics in the plane. However for electric planes, we also use
the batteries to power the motor. They are the chemical fuel tanks and
fuel pumps that store and deliver the energy we use to fly.

These battery packs are made up of cells which act as chemical storehouse
for electrical energy. When multiple cells are joined together we call this
a battery or battery pack. There are a variety of battery types. Each has
advantages and disadvantages that we will discuss.

Battery Types

At the time of this writing, there are three commonly used rechargeable
types of cells. They vary by the chemical mix that is used to
hold and deliver the electricity.

Nickel Cadmium, NiCd, have been in around the longest. Still used for receiver
packs but are no longer commonly used as motor packs.

Nickel Metal Hydride, NiMH came in to use later and are still in use
today for receiver packs. While still used for motor packs their popularity
is fading compared to the lithium based cells. .

Lithium cells are typically lithium polymer, LiPoly or LiPo, or the Lithium Ion
cells. These are the newest breed of chemical cells. They are starting to
be used as receiver packs but probably represent the most popular battery
type for powering electric airplane motors.

NiCd packs have the lowest power to weight ratio. That is to say that, for
a given electrical capacity they will weigh the most of the three types.
Each NiCd cell is rated at 1.2 volts.

Nickel Metal Hydride, NIMH, packs hold about 40-60% more capacity per ounce
than NiCds. So, for example, a 800 mah NiCd pack might weigh 6 ounces while
an equivalent capacity NIMH pack might be 4 ounces. Each
NIMH cell is rated at 1.2 volts, the same as NiCd cells.

In many ways NiCd and NiMh cells are very similar in their application. So,
as a shorthand, I am going to start to refer to NiMH and NiCd as NiXX when
what I am saying applies to both. I hope this does not lead to confusion on
the reader's part.

Lithium packs are the lightest for their capacity. For this reason they have become
the standard for most electric airplane applications. They typically hold 3 or
more times as much electricity per ounce as compared to NiCd packs. For
example a 6 cell, 7.2V 2100 MAh NiCd pack might weigh 13 ounces while a 2
cell 7.4V Lithium pack of the same capacity will be about 4 ounces.

Because much of our RC electronics have been based on 4-5 cell NiXX packs
they are tuned for 4.8-6V receiver packs. However Lithium packs are 3.7V so
one cell is a bit low to power most receivers and two cells at 7.4V is a bit high.

So Lithiums have not been in common use for receiver packs used in gliders or glow powered
planes. Some micro plane electronics systems have been designed for 1 cell
lithium packs and the newer generation of electronics for the rest of the
market are being retuned to accept 1-2 cell Lipo receiver packs. But be careful.
Your receiver might be able to handle a 7.4V 2 cell lipo pack but your servos may not.

The newest generation Lipos and LiOn packs can now deliver high currents. And
many lithium packs rated 20C or higher can be charger higher than the traditional
1C maximum that has been standard for Lithium packs. They are growing in
popularity as the charge/discharge rates improve and the prices come down.
Each Lithium cell is rated at 3.7 volts.

BATTERY CHARGING SAFETY

Any battery pack can fail or overheat so always charge your batteries in a fire proof area.
While most cautions are directed to Lithium type packs, I have never had a problem with a
Lithium pack. But I have had a NiMh pack catch fire. So no matter what you are charging
take precautions.

If the links have gone out of date, just do a yahoo or Google search on Lipo Sack and you
will find a variety of offerings. Their design is to contain any flame or burning that might result
from a failed pack during charging.
If you follow proper charging procedures and use a
quality charger then the chances are very slim that you will have a problem. But just like the
seatbelts in your car, you put them on to be prepared for the unexpected. And use these for
all battery packs, not just lipos. I keep a coffee can on my work bench and all batteries get
charged in the coffee can or in a lipo sack, just in case.

Pack Configuration

Unless stated otherwise, we join the cells into packs by joining them in
series. In series we add the voltage of each cell so that a 6 cell NiXX
pack will be rated at 6 X 1.2 volts or 7.2 volts. With lithium packs, which
are rated at 3.7 volts per cell, it would take two cells to create a
comparable 7.4 volt pack.

Clearly if your instructions say that your motor can use a 7 cell pack, it
would be important to know if that is 7 NiXX cells or 7 Lithium
cells as the voltages would be very different. A 7 cell NIMH or NiCd
pack would be 8.4 volts. A 7 cell Lithium pack would be 24.9 volts.

While it is unusual to combine NiCd or NIMH packs in parallel to increase
capacity, it is quite common with Lithium packs. This has spawned the xSyP
designation, were x is how many Lithium cells are connected in series and y
is how many groups of these cells are connected in parallel. So a
3S2P pack would have two groups of 3 cells. This allows us to deliver
higher amperages at the same voltage, or to provide more capacity for
longer flights at the same voltage. The xSyP designation is most commonly
used with Lithium packs. I don't recall ever seeing this used with NiXX
packs.

Battery Chargers

When charging your battery packs you MUST use the right kind of charger or
you will damage the cells. Using the wrong charger, especially
with lithium cells, can actually lead to a fire or an explosion. So be sure that you
have the right charger for the kind of cells you are charging. Some
chargers are specific to one kind of cell while some can charge two kinds
and some can charge all three. Make CERTAIN you know before you charge or
you could put your model, your car, your home or your personal safety at
risk.

I hope this has been helpful. Below are additional resources for your
further reading.

Lithiums are great, but they benefit from a little extra care. We have seen that packs
with two or more cells can get out of balance. That means that one cell tends to
rundown lower or tends to charge higher. Since charging through the power port
that connects to the ESC only reads the total pack voltage the charger will charge
the pack to the expected voltage. For Lipoly packs that would be 4.2V per cell.
Therefore, when charging through the power port, the charger will take a 3 cell Lipo to
12.6V, regardless of the individual cell voltages. But if one cell is low and one is
high, that could result in one cell perhaps being charged to 4.3V or one being charged to
4.1V, for example.

Over many cycles this difference will build up. The most benign outcome is a loss of
pack performance. A more serious outcome could be that the low cell will drop below
the critical 2.5V level on discharge and be damaged, rapidly degrading the pack.
The more serious issue could be that one cell gets seriously over charged getting
well above the desired 4.2V top charge. This can result in pack failure or can cause the
over charged cell to "vent with flame". This is ungood. :-O

Balancers

One way to balance your battery packs is to use a balancer after charging. This will bring the
packs into balance to maintain an even charge across all cells. To use these balancers you
need a compatible balance plug on the pack. Assuming you have this arrangement,
a balancer can help prevent the above situation. If you are happy with your charger and
don't feel the need for a new one, a balancer is a good investment. They run from $10 to $30
with a variety of features.

The balancing benefit is significant but it need not be critical to every charge cycle. Packs
don't go out of balance THAT fast. It might happen over 5 cycles or 10 cycles and it builds
up over time. So using a non-balancing charger is fine as long as you balance the pack
every few charges.

Note that a balancer can only drain power so it does reduce the overall charge level of the pack,
it does not bring up the low cells. But I don't think that is a big deal.

Chargers with built in balancing

There are two features being discussed here, charging and balancing.

Some are chargers combined with balancers. They charge the pack to the desired
level, then the built in balancer bleeds down the high cell and charging can continue.
This is a good combination. It saves you from having to do this with a separate device.
This type of charger provides the very significant value of keeping your packs in balance
automatically. This leads to longer life, and better performance. And it has some safety
benefits in that it prevents one cell from being over charged.

Balanced Chargers

Then there are balancing chargers that charge each cell individually during the charge
cycle. The CellPro 4S, for example, charges each cell individually during the charge cycle.
If one cell is a little slower than the others the charger compensates so higher rates can be
tolerated, or so the charger companies claim. The older CellPro 4S that I have has a safe
charge cycle that charges at up to 1.4C. This is a side benefit of the balanced charge process.
The newer Cell Pro 4S charges at up to 3C. If charging your packs faster,
safely, is important to you, then these types of balancing chargers are a good value. CellPro is not
the only one but it is a good example. So, from that respect, certain chargers, let's call
them balanced chargers, bring more benefits than just balancing.

Practical use

I have 5 lipo packs with CellPro balance taps. Most of the time I charge them on my CellPro
charger but I also charge them on my Triton charger and on an AC wall wart Lipo charger.
Only the CellPro balances, but the packs get on it every few cycles so they will be balanced
on the next charge cycle. And only the CellPro charges at the higher rate. The others are
limited to 1C and I will not push them.

Cold Weather Cycle

I don't know if this is a common feature but the CellPro 4S also has a cold weather cycle.
It actually detects the temperature of the surrounding air. If it is below a certain level, it only
charges the cells to about 95% of full charge. This has very little impact in practical use but
it provides a safety effect. If you were to charge a lipo pack at the field, say at 30 degrees,
then not use it and take it home, as it warmed the cell voltage would rise, potentially taking it
over the desired 4.2V level. I can not say how serious a concern this may be, but it seems
to make sense that it could present an unrecognized problem. This charger accounts for it
automatically. I am sure there must be others that do it as well.

I do feel the balancing chargers are better than balancers, BUT not enough that it should be a
big concern if you don't feel you want a second charger or the higher charge rates that some
of the newer ones can offer. But understanding the benefits of balancing IS important.

This is not totally unique to electric flight, but since many new electric pilots are trying to self train, it sorta fits.

SIX KEYS TO SUCCESS
by Ed Anderson
aeajr on the forums

Whether you have a coach or you are trying to learn to fly on your own, you
will need to be mindful of these six areas if you are going to become a
successful RC pilot. After years of working with new flyers at our club,
and coaching flyers on the forums, there are a few things I have seen as the
key areas to stress for new pilots. Some get it right away and some have to
work at it. They are in no particular order because they all have to be
learned to be successful.

WIND
Orientation
Speed
Altitude
Over Control
Preflight Check

1) Wind - The single biggest cause of crashes that I have observed has been
the insistence upon flying in too much wind. If you are under an instructor's
control or on a buddy box, then follow their advice, but if you are starting
out and tying to learn on your own, regardless of the model, I recommend
dead calm to 3 MPH for the slow stick and tiger moth type planes. Under 5
MPH for all others. That includes gusts. An experienced pilot can handle
more. It is the pilot, more than the plane, that determines how much wind
can be handled.

The wind was around 10 mph steady with gusts to 12. That was strong enough
that some of the experienced pilots flying three and four channel small
electric planes chose not to launch their electrics. This new flyer
insisted that he wanted to try his two and three channel parkflyers. Crash,
Crash, Crash - Three planes in pieces. He just would not listen. Sometimes
you just have to let them crash. There is no other way to get them to
understand.

Many parkflyers can be flown in higher winds by AN EXPERIENCED PILOT. I
have flown my Aerobird in 18 mph wind (clocked speed) but it is quite
exciting trying to land it.

Always keep the plane up wind from you. There is no reason for a new flyer
to have the plane downwind EVER!

2) Orientation - Knowing the orientation of your plane is a real challenge,
even for experienced pilots. You just have to work at it and some adults
have a real problem with left and right regardless of which way the plane is
going. Licensed pilots have a lot of trouble with this one as they are
accustomed to being in the plane.

Here are two suggestions on how to work on orientation when you are not
flying.

Use a flight simulator on your PC. Pick a slow flying model and fly it a
lot. Forget the jets and fast planes. Pick a slow one. Focus on left and
right coming at you. Keep the plane in front of you. Don't let it fly over
your head.

FMS is a free flight simulator. It is not the best flight sim, but the
price is right and it works. There are also other free and commercial
simulators.

The links below take you to sites that provide cables that work with FMS.
If your radio has a trainer port, these cables allow you to use the trainer
port on your radio to "fly" the simulator. This is an excellent training
approach.

An alternative is to try an RC car that has proportional steering. You
don't have to worry about lift, stall and wind. Get something with left and
right steering and speed control. Set up an easy course that goes toward
and away from you with lots of turns. Do it very slowly at first until you
can make the turns easily. Then build speed over time. You'll get it! If
it has sticks rather than a steering wheel even better, but not required.
Oh, and little cars are fun too.

3) Too much speed - Speed it the enemy of the new pilot but if you fly
too slowly the wings can't generate enough lift, so there is a compromise
here. The key message is that you don't have to fly at full throttle all the
time. Most small electrics fly very nicely at 2/3 throttle and some do quite
well at 1/2. That is a much better training speed than full power. Launch
at full power and climb to a good height, say 100 feet as a minimum, so you
have time to recover from a mistake. At 100 feet, about double the height
of the trees where I live, go to half throttle and see how the plane
handles. If it holds altitude on a straight line, this is a good speed.
Now work on slow
and easy turns, work on left and right, flying toward you and maintaining
altitude. Add a little throttle if the plane can't hold altitude.

4) Not enough altitude - New flyers are often afraid of altitude. They
feel safer close to the ground. Nothing could be more wrong.

Altitude is your friend. Altitude is your safety margin. It gives you a
chance to fix a mistake. If you are flying low and you make a mistake ....
CRUNCH!

As stated above I consider 100 feet, about double tree height where I live,
as a good flying height and I usually fly much higher than this. I advise
my new flyers that fifty feet, is minimum flying height. Below that you better
be lining up for landing.

5) Over control - Most of the time the plane does not need input from you.
Once you get to height, a properly trimmed plane flying in calm air will
maintain its height and direction with no help from you. In fact anything
you do will interfere with the plane.

When teaching new pilots I often do a demo flight of their plane. I get the
plane to 100 feet, then bring the throttle back to a nice cruising speed. I
get it going straight, with plenty of space in front of it, then take my
hand off the sticks and hold the radio out to the left with my arms spread
wide to emphasize that I am doing nothing. I let the plane go wherever it
wants to go, as long as it is holding altitude, staying upwind and has
enough room. If you are flying a high wing trainer and you can't do this,
your plane is out of trim.

Even in a mild breeze with some gusts, once you reach flying height, you
should be able to take your hand off the stick. Oh the plane will move
around and the breeze might push it into a turn, but it should continue to
fly with no help from you.

Along this same line of thinking, don't hold your turns for more than a
couple of seconds after the plane starts to turn. Understand that the plane
turns by banking or tilting its wings. If you hold a turn too long you will force
the plane to deepen this bank and it will eventually lose lift and go into a
spiral dive and crash. Give your inputs slowly and gently and watch the
plane. Start your turn then let off then turn some more and let off. Start
your turns long before you need to and you won't need to make sharp turns.

I just watch these guys hold the turn, hold the turn, hold the turn, crash.
Of course they are flying in 10 mph wind, near the ground, coming toward
themselves at full throttle.

6) Preflight check - Before every flight it is the pilot's responsibility to
confirm that the plane, the controls and the conditions are correct and
acceptable for flight.

Plane - Batteries at proper power
Surfaces properly aligned
No damage or breakage on the plane
Everything secure

Radio - Frequency control has been met before you turn on the radio
A full range check before the first flight of the day
All trims and switches in the proper position for this plane
Battery condition is good
Antenna fully extended
For computer radios - proper model is displayed
All surfaces move in the proper direction

Conditions - No one on the field or in any way at risk from your fight
You are launching into the wind
Wind strength is acceptable ( see wind above )
Sunglasses and a hat to protect your eyes
All other area conditions are acceptable.

Then and only then can you consider yourself, your plane, radio and the
conditions right for flight. Based on your plane, your radio and local
conditions you may need to add or change something here, but this is the
bare minimum. It only takes a couple of minutes at the beginning of the
flying day and only a few seconds to perform before each flight.

If this all seems like too much to remember, do what professional pilots do,
take along a preflight check list. Before every flight they go down
the check list, perform the tests, in sequence, and confirm that all is right.
If you want your flying experience to be a positive one, you should do the
same. After a short time, it all becomes automatic and just a natural part
of a fun and rewarding day.

I think ready-to-fly airplane packages are great. This is how I started flying.
If I had been required to build a kit to begin my flying experience I would
never have gotten into the air. Now, after thousands of flights and almost
years of flying, I have expanded to 20+ planes, multiple radios and all kinds of
tools and things. I am having a ball. But there are things I know today that
would have helped me with my first plane. Let me pass on some tips.

Regardless of the plane, RTF or not, it is the pilot's responsibility to insure
that the plane is flight ready. If you put a plane in the air without checking
it, without following the instructions, any problems that follow, any damage
that is caused is your fault and responsibility. It does not matter if the
plane is defective, if you did not check it, any damage that occurred is your
fault. I can't make it any clearer. No full scale pilot would takeoff without
checking everything. You should do the same.

READ THE INSTRUCTIONS!

There is a manual or instruction sheet that comes with your plane, read it! I
read the manual several times on anything I get. It took the manufacturer time
and money to create it. I contains important information. Some instruction
sets are poorly done and some are very good. In either case, READ! If there
is a video included, watch it. It was put there to help you. Take advantage
of that help.

If they have a web site about the plane or product you purchased, visit the
site. Sometimes there is an FAQ, frequently asked questions page. Sometimes
there are additions to the instructions that have been added since yours was
packaged and shipped. And sometimes there are coupons, or specials for owners.
Go, look and see, and benefit from the manufacturer's web site.

RTFM

I often post this in my notes on the forums, "RTFM". To put it politely, it
means, " Read The Friendly Manual".

I have read so many trouble reports by new flyers. They crash, they have
problems and are angry and upset. Why was this happening to them? Often, the
answers were all in the instructions.

We had one club member who used to buy RTF planes, show up at the field and ask
me how to get them set-up and flying. I would ask him for the instructions.
"Oh, I left those home." So I sent him home to get them. No matter how
experienced I might be, unless I have this plane, I check the instructions.

He brought a computer radio to a meeting and asked me to show him how to use it.
"Sure, where are the instructions?" He left them home. I could not help him as
I had never seen that radio before.

Needless to say, he crashed and crashed and destroyed things. Fortunately for
him he had the money to do this. But he occasionally created a safety situation
and we had to "advise" him to change his ways. He has yet to become a
successful flyer. He is still a nice guy and I hope some day he will be
successful, but he needs to follow instructions.

THINGS TO NOTE WHEN YOU READ THE MANUAL

1) Does the plane need to be balanced, or does the balance need to be checked?

2) Are there linkages to be connected? Do they need to be adjusted? How do you
adjust them?

3) Is there tape or glue to be added. Is there covering material to be removed?

4) Do the batteries need to be charged?

5) Do they recommend some kind of "break-in" procedure?

6) What is the proper range check procedure for the radio system?

7) What is the working range of your radio system?

8) How do you adjust the surfaces to get the plane to fly correctly? Are they
moving in the correct direction?

9) What is the proper placement of the battery and how is it moved to adjust
balance?

10) Is there a maximum recommended voltage that can be safely accepted by the
ESC?

11) What wind speeds are recommended for new flyers?

12) How much space is recommended to fly this plane?

13) Who do you call if there is a problem? Do you call the hobby shop or the
manufacturer? Is there a web site?

14) Are there repair tips? What kind of glue can you use? Where can you get
replacement parts?

15) What channel is your plane using and how do you avoid channel conflict?

ASSEMBLY TIPS

Often, in order to meet a packaging goal or to keep the shipping weight down,
the manufacturer will expect you to do something or to add something. These are
usually common household items like tape or glue. In some cases the plane's
balance has to be checked and/or adjusted. They may include weights, or you
may need to buy weights, but coins work too. A dime is about .1 ounces and a
quarter is about .2 ounces. Coins can actually be cheaper than buying weights.

It is common to have to mount the tail and the wing. Are there alignment marks
or procedures that you are to follow? Do you have to remove covering material
so the glue will hold properly? How many rubber bands are needed to hold the
wing properly? Don't use less than the recommended number of rubber bands.

My Great Planes Spirit 2M glider came RTF, including the radio system. This was
my second plane after my Aerobird. The Aerobird did not need to be balanced,
the Spirit did. If I had tried to fly it without balancing it first I would
likely have broken it badly on the first flight. It took four ounces of weight
in the nose to get to balance properly.

A friend's RTF was brought to the field so we could help him. Following the
instructions we did a range check and found there was a problem with the radio
system. No problem! He packed it up, took it to the hobby shop and they
exchanged it immediately. He was back at the field in an hour. It was clear it
had not been flown so there was no question of flight damage. If he had flown
and crashed it, they could have easily refused to replace it, and they would
have been right, as crash damage is not covered under warranty. It was the
pilot's job to make sure the plane was flight ready.

FLYING TIPS

Often RTFs come with flight instructions and tips. One of the most important to
follow is related to wind. Many planes, especially two channel planes, do not
handle wind very well, especially in the hands of an inexperienced pilot. If
you don't know this, you could loose your plane, or worse, you could hit someone
or cause damage. What wind speeds are recommended, especially for new pilots?

Sometimes the plane will "porpoise" or tend to roll, or want to dive. Is it you
or is it the plane? The instructions may tell you.

Once the pilot has become comfortable with the plane, there may be adjustments
that can be made to make the plane more responsive. Sometimes it is that switch
on the radio, or a button you need to push, that goes from mild to wild. Or
maybe you have to turn something on the linkage, or move the linkage to a
different hole. Go back and read the manual for the proper procedures to make
those adjustments.

SUMMARY

Just because the plane says ready to fly, don't take that literally. Compared
to a box of sticks and a tube of glue, it is ready to fly. However there are
often set-up procedures, or assembly steps that needs to be done. It is best
to read the instructions to see how to do them correctly. You will have a much
better flying experience and your plane will last longer.

THE ROLE OF THE BEC IN YOUR ELECTRIC PLANE
by Ed Anderson
aeajr on the forums
Updated 1/24/15

In the world of electric motors the electronic speed control, ESC, takes the
place of the throttle servo used on fuel powered planes. It regulates the speed of the
motor by pulsing the power to the motor to achieve the desired motor speed.
However most ESCs also have two other functions, the LVC and the BEC.

The LVC, low-voltage-cutoff circuit, will cut power to the motor and preserve
power to the radio system so you can land your plane safely when the motor
battery is getting too low. In the case of lithium batteries, the LVC, can also
save your battery packs by preventing them from getting too low. If you started
with NiXX packs and have switched to lithium packs, be sure your LVC is set
properly or you could damage your lithium packs.

The BEC, the battery elimination circuit supplies power to the receiver and the
servos. It is the BEC that will be the main focus of this discussion.

The name, battery elimination circuit, comes from the fact that, in the "old
days" of electric planes, you had a battery pack to power the motor and another
one to power the receiver. In order to save weight, the BEC was introduced to
eliminate the need for that receiver battery pack.

BEC, battery elimination circuit, is a generic term that applies to all circuits or
devices, whether in an ESC or as a separate device, that step the
voltage to the desired level. You could also call them voltage regulators.
They take the power from a battery pack and reduce the voltage to the level
desired. For example, an 11.1 V 3S lipo pack gets stepped down to 5V to run
your receiver and servos. Most are fixed but some can be set for the desired
output voltage.

There are two types of BEC in common use, linear and switching.
Whether you do it with a switching or a linear BEC the effect is about the
same. I am not aware of any reason to believe that one is more reliable than
the other or that an external BEC is in any way better than one integrated
into your ESC. The critical issue is the sizing of the BEC to meet the
amperage and voltage needs of your equipment.

It is worth noting that linear BECs are more commonly used with lower
voltage battery packs. That is because the linear BEC uses a resistance
process to drop voltage from, say 11V to 5 V and this generates heat.
Nothing to be concerned about but that is how it works. So once you get past
a 4S lipo or a 12S NiXX pack the step down becomes enough that most
manufacturers go to the switching BEC design. This uses the same type of
switch on/off process that your ESC uses to regulate the speed of your
motor.

There is nothing inherently more or less reliable in either design from a
practical point of view. It is just a matter of the most appropriate device for
the use case. I would have no hesitation to use a linear BEC
on any pack for which it is rated. Nor do I have a big preference for
external vs. internal BECs.

One thing to note is that linear BECs are rated for output based on input
voltage. So, a linear BEC might be rated for 3 amps output when used on a
2S pack but only 2 amps output when used on a 3S pack. Again, that is related
to the resistance method. The higher voltage drop generates more heat so
they derate the device for safety. But if you only need 1 amp, who cares?

The biggest issue we face when talking about BECs is that we really don't
know what we need in amperage. Do you know how many amps any given servo
draws? Did you know that the number goes up when the servo is under load?
And, of course, the total amp load goes up if you are moving more than one
servo. And a stuck servo's amp draw can go very high.
Typically we evaluate the size of be BEC based on the number of servos,
what has worked in other planes or what the MFG recommends.

As an example, the Radian Pro Bnf has 6 micro servos and a Spektrum receiver.
It was originally shipped with a BEC rated at 750 mah. Now, most people would tell you that
that is not a large enough BEC for 6 micro servos. But there were a LOT of
Radian Pros shipped with them and most flew just fine. Later they shifted
over to a larger BEC, 1.5 amps I think, to provide a greater margin for safety.

Note that the voltage rating for the ESC may be different than the voltage
rating for the BEC. Your ESC may be rated for 6S/22.2V but the BEC may have
to be disabled over 12 volts and you will have to power the receiver separately.
If you don't take note of this and pop in a 6S lipo, your ESC may be fine
but your BEC may be heading for a failure, resulting in a crash.

If you are flying an RTF or "receiver ready" model, you can be confident that the
BEC chosen is appropriate when used with the recommended battery pack. As
an example, the manufacturer of the plane may
designate that the plane takes an 8.4V pack. At that voltage the included BEC
may be fine. However, if you decide to pop in a three cell lipo, a problem may
only be a launch away. The BEC may do fine for a couple of flights, or maybe 5
minutes or may fail 100 feet out, and down you go.

We also have the variable of which servos are being used. Different servos draw
different amounts of current. If the current draw gets too high, the BEC will
overload causing a shutdown of the BEC. This protects the BEC and
prevents a fire, but cuts the voltage to the receiver. The net effect is that
you lose all power to the radio system and you lose control of the plane.

In the case of an overheated BEC, if there is enough cooling air going through
the plane, the BEC may come back quickly as it cools. This could look like a
radio glitch, but it could be the BEC operating on the edge of total failure.
If your ESC is very hot when you land, the cause could be the BEC operating at
the edge of its capacity. When we see these glitches, we often think the
problem is the radio system, but in fact the cause is power to the receiver.

When we were switching from 72 MHz radios to 2.4 GHz radios a lot of people thought
their 2.4 GHz receivers were failing but what was actually happening was that the
2.4 GHz receivers pulled more power, more amps, which overloaded the BEC in
the plane. If the BEC was just adequate for the 72 MHz receiver, which may have
only needed 20 mA and you put in a receiver that needed 100 mA then a BEC that
was just adequate for the 72 MHz receiver could cut out with the 2.4 GHz receiver.
We are more aware of this now and this has become less and less of a problem.

A CASE STUDY

This pilot was flying a new Spektrum 2.4 GHz system. All was fine till the plane
suddenly went dead and crashed. All sorts of speculation were offered about what
the cause could be and much of it was focused on the Spektrum 2.4 GHz system.
After the plane was recovered, everything seemed to work OK so it must have been
a radio hit, right? However, due to the diligent work of the pilot, it was
determined that the BEC had failed due to overload. You can read the actual
account at this link in posts 2986 to 3006.http://www.rcgroups.com/forums/showt...04621&page=200

This is not the only account of this type that has been reported, but this was
one that was worked out over a short time with a very clear outcome. Note also
that the pilot had to run his test for several minutes before the failure
appeared. Thus, everything seemed fine at first; it seemed that the BEC was
handling the load. But over several minutes' heat built up in the BEC. Combine
this with the heat from the motor and the battery and, perhaps not enough
cooling airflow and the BEC shut down.

BE COOL FOOL!

With good airflow a BEC overload may be avoided. Regardless of what radio
system you are using, make sure you have enough cooling air going through your
electric plane. This is especially true of foam planes as the foam acts as an
insulator. You may have a cooling air vent in the front somewhere, but the heat
can't get out unless there is an exit air hole large enough to allow good
airflow. If you are pushing the limit on any part of your power or radio system,
not enough cooling air can cause damage or failure to your motor, ESC, BEC or
battery packs.

How you fly your plane can also cause heat build-up. For example, an Easy
Glider that has the motor run 1 minute to get to altitude then glide might have enough airflow
to eliminate the built up heat. But if you run the motor constantly for 10 minutes,
the heat build up could be enough to cook your BEC, your battery pack, or some
other part of the plane.

Be cool fool, and make sure you have enough airflow in your plane. If your
battery is very hot, or if your ESC is very hot, you may need more cooling.

OTHER CAUSES OF BEC PROBLEMS

You could be configured properly. Your BEC may be rated to handle your servo
count and you could have plenty of cooling air but still have problems. If you
have a servo push rod that is dragging or is otherwise placing a high load on
the servo, this can increase the amp draw of that servo. If that servo gets
stuck, the amp draw will go way up!

Servo loads are expected to be variable. A servo will move, put a load on the
BEC then come back to neutral and the current draw will drop. In between loads,
the BEC has a chance to cool. However a jammed servo will draw a lot of power
and that draw will be constant. You can see why it is very important that your
servos move freely, without binding. Check those control rods for kinks,
obstructions or things that could get in the way.

ENTER THE COMPUTER RADIO

In the past it was common to have 2 ailerons run off of one servo, so three
servos were typical of a 4-channel electric plane. With more and more people
using computer radios, there is a tendency to put 2 servos on the ailerons
meaning more load on the BEC.

Also, with a computer radio it is easy to add a little aileron to rudder mixing,
moving 3 servos at once. Now add a little up elevator in the turns and all four
servos are pulling power. Go to a full house electric sailplane, with flaps
following ailerons, rudder mixed in and a little up elevator in the turn and you
now have 6 servos, all moving at once. We begin to see how the BEC can become
challenged to keep up.

WHAT IF YOU NEED MORE?

If you need more power than the integrated BEC in your ESC can supply, or if
your motor battery voltage is higher than the BEC can handle, you will need to
disable the integrated BEC and put in a separate receiver pack or a separate
BEC. Many companies make after market BECs that can handle these higher
voltages or higher servo loads.

Remember there are two different types of BECs. Both work but they work
differently. Most, but not all aftermarket BECs seem to be switching BECs,
but be sure to read the instructions. If the amp output is different based on
battery voltage then it is a linear BEC. Nothing wrong with that, just be aware
of the rating for the voltage battery pack you plan to use.

Regardless of what type you have, follow the instructions carefully or risk
losing your plane. And be sure to provide plenty of cooling air.

The ESC is the heart of your electric power system. The BEC is the part of the
ESC that powers your radio system. Keep it cool and make sure you read the
instructions so you don't overload it. Forget these tips and you may be
picking up pieces of your plane, wondering what caused that crash.

I received several requests for an article about the characteristics of a good first plane. As many new electric pilots are also self trainers, they don't have the benefit of an instructor. Hopefully this will be helpful.

Ed Anderson

=========================================

The Mythical Best First Plane
by Ed Anderson
aeajr on the forums

If you run a search on any of the RC forums you will find many posts that ask
for advice on the best first plane for them to get. The purpose of this
discussion is to show that there is no perfect first plane. But there are
things that can be taken into account to help someone pick an appropriate
plane.

Be advised that this discussion will be based on my personal experiences, my
bias, my prejudice, my research , what I have observed, and what I have been
told. That is exactly the basis that every one uses when they give you their
advice. So take this and mix it in with other advice you trust, as no one
person has the answer, only opinions based on our knowledge set.

Go and read, so you can build on what you read here. Then make an informed
decision and go with it. And when you are greeted by the first all knowing
guy who tells you that you made a mistake, you will be able to explain your
reasons, the considerations and the goals upon which you purchased that plane.
And if he doesn't agree? That's OK, we are all entitled to our opinions.

First Consideration - How are you going to learn?

An Instructor - The best, but not the only path to success

If you plan to learn to fly under the close guidance of an instructor, then do
NOT go and buy a plane. Go to your instructor and ask what they suggest.
Learning under an instructor is the best way to learn to fly. That
knowledgeable guide is going to take you through planned steps that will
impart skill and knowledge. So the best first plane is the one that allows
that instructor to do that. Your best first plane is the one s/he is most
comfortable using.

No one else's opinion matters as you have placed yourself in their hands and
should follow their lead. Otherwise why are you working with an instructor?
This opinion comes from a guy who has never worked under the close guidance of
a flight instructor but received much coaching from helpful and willing members
of the club I joined. But any journey of learning is best started with a
knowledgeable guide, and when you engage a guide, you follow them. Nuff said
about that!

A Coach - Much better than going it alone

A coach is an experience friend or club member who is willing to give you some
time, provide some assistance and point you in the right direction from time
to time. However they are not going to take on the close training
responsibility of an instructor. They will help, but you will be doing a lot
of the learning on your own. This is how I learned.

To be a coach, I feel the person has to spend some time with you on the field.
Perhaps they preflight your plane. Maybe they take it up for the first flight
to make sure it is OK. They may or may not use a buddy box. But the key is
that they will give you some help. Having a coach is a wonderful thing.
Things that are a mystery to you can be made clear in a moment by that helpful
coach.

The key is that you take on a lot of responsibility as you will be on your own
much of the time and there is probably no formal program that is being
followed. If you can't find an instructor, try to find a coach.

An Advisor

I and many of the people who post on these forums are trying to take on the
role of advisor. We can't be there with you but we can explain a few things,
and point you to good sources. We can tell you what has worked for us. A
coach is much better but you can have coaches and advisors and you can benefit
from the multiple sources of information. If you have an instructor, you can
ask for clarification from advisors but you should always take your lead from
your instructor. Whether a paid or not, they have made a commitment to you.
You have to do the same.

On Your Own

Here I mean that you bought something, read the instructions and tried to fly
it. Can you be successful? Sure! But the chance of success goes up as you
add levels of help. Find advisors, seek coaches and get an instructor if you
can. You are more likely to progress faster and your planes are more likely
to survive your progress. Flying is not a simple or obvious thing. It took
intelligent people thousands of years to learn how to do it. There is no
disgrace in you taking advantage of some of that previous experience and
knowledge. Get some help if you can.

Now to the Plane -

WING DESIGNS

High, Mid or Low

Broadly speaking, airplanes have one of three wing locations. They are
either high wing, mid wing or low wing. This does not include things
like flying wings or delta wings. These don't have a fuselage in a
conventional sense. And, while there are people who learn to fly on
these designs, I don't consider them the first choice for
beginner/trainer planes.

Most people will agree that the better choice for beginner/trainer
planes are high wing designs. The reason is simple, with the wing high
and the fuselage hanging below, the plane tends to be more stable and
self righting. This can help keep a new pilot out of trouble.

Mid wing and low wing planes are typically less stable as the weight of
the fuselage is mounted around or above the wing. These planes are
typically more agile and aerobatic than the high wing planes. That P51
Mustang you saw at the hobby store is a good example. It may be a cool
looking plane but it isn't really the best choice for a first plane.
That is why the fighter pilots who flew it in combat started on
something else when they were learning to fly. It might be a good idea
if you did the same. They make good second or third planes once you have
mastered the basics of flight.

Dihedral

You will notice that some planes have wings that are basically straight.
That is, they come straight out from the fuselage. Others have an
upward angle where the end of the wing is higher than the root, the part
that attaches to the plane. This is called dihedral. On some planes
the upward sweep goes through two or three upward angles. In this case
we say the wing is polyhedral, or having many dihedral angles.

Wings with some dihedral tend be more stable and self righting than flat
wings. Wings with flat designs tend to be more responsive and will tend
to go where you put them, but also tend to stay there. This means that
if you bank the plane to make a turn, you better remember to bank it
back to level or it will stay that way. A banked wing will tend to lose
altitude if not managed properly. A plane with dihedral in the wing will
tend to return to level flight if you release the sticks.

In fact, when I am helping new flyers, if their plane has a fair amount
of dihedral, I will often advise them to release or center the stick if
they get into trouble. While not always the right thing to do, most of
the time the plane will right itself if it has enough altitude and
enough dihedral in the wing. It sounds funny but sometimes the planes
know better than we do when it comes to flying. We have to teach people
to let the plane fly.

Whether you are flying glow, gas, glider or electric, having some
dihedral in the wing of your trainer will help it to stay stable and
level during your early flights. To some extent dihedral will tend to
"fight" roll based aerobatics like inverted flight knife edges and the
like. However, when you are trying to master take-off, landing and
straight level fight, this is less of a concern.

ENGINE LOCATIONS

Many people expect the motor and propeller to be on the front of the
plane. However there are many places where the propeller can be
located. It can be a pull or push design. It can be in front or in
back. And while pure sailplanes don't have motors, e-gliders use a
motor as a launching system to get into position to look for lift.

There is much to be said for a pusher design on a first plane. On
take-off and during flight, the engine location may not matter on that
first plane. However when you come in for a landing, having the engine
and propeller high and out of the way can be very helpful. You are less
likely to hit the prop and, if you do come in hard on the nose, your
repairs are more likely to be restricted to fixing fuselage damage and
less likely to involve fixing or replacing the motor and/or propeller.

I don't have a problem with front motor designs as they are clearly the
most common. However I think that the pusher design has some advantages
for new flyers.

POWER SOURCE

Today RC aircraft are powered in a variety of ways, each having its
advantage. While there are good first/trainer planes in each category it
is worth a moment to explore the different ways to power your RC plane.

Gliders

Pure gliders or sailplanes have no motors. They achieve flight through
some sort of launching system. Once in the air they may simply glide
down or they may be designed for the pilot to look for natural sources
of lift such as thermals or slope lift. Clearly you have no fuel cost
and your battery needs are extremely modest. So the cost of fuel,
chargers, motor packs and the like just don't show up.

If this is a thermal glider, you will typically need some kind of
launcher. It might be a good arm toss for a hand launched/discus
launched glider or it might be a hi-start, an elastic system that
typically costs under $100 an lasts for years. If this is a slope
glider, then your fuel comes from natural air flow, but you have to find
the right location.

First gliders tend to be in the 1.5 to 2 meter, 60 inch to 80 inch range and
weight between 8 and 38 ounces. They typically fly fairly slowly.
This slow flight gives the pilot the advantage of having more time to
think and react to the plane.

The one down side of gliders is that they don't have the instant power
nature of powered planes. But their silent flight and low operating
costs can make them very attractive to new flyers.

Electrics

For electric powered aircraft, including e-gliders, you use a
combination of an electric motor and battery system to get your plane
into the air. Electric power has become very popular as battery and
motor technology has advanced. Today's sophisticated electric planes
can rival the performance of traditional fuel powered planes.

Electrics are quiet, clean and very dependable. On the other hand you have the
up front cost of battery packs, and battery chargers. If you allocate the cost
of these items over their useful life, electric flight is quite economical.

Electric power also lends itself to small planes and indoor use. Today you can
buy kits, ARFs or RTF electric planes that weigh 1 ounce or less. The broader
"parkflyer" weighs from 8 ounces to about 32 ounce and can be flown in areas
the size of baseball, football or soccer fields. Others require more room.

Some electrics can fly very slowly which allows them to be flown
indoors. Many of these "slow flyers" make excellent first or trainer
planes, even outdoors if you wait for calm weather.

Since you don't have the vibration inherent in internal combustion power
system, electric planes tend to be build lighter, however once you add
the battery system back in, an electric plane tends to be similar in weight to
comparable fuel planes, especially if they have modern brushless motors and
lithium batteries.

It should also be noted that over the duration of the flight, the available
power will start to drop off as the battery pack runs down. So maneuvers that
can be done
in the beginning of the flight might be difficult near the end of the flight.
This drop off will probably always exist but today's battery technology is
making this less and less of an issue as flight times extend from the 5 minute
flights of a couple of years ago to the more common 10-20 minute flights of
today.

One last point on electric power. Because it is clean and quite,
electric planes can sometimes be flown in locations where fuel powered
planes might be denied. This factor alone has probably been a key
contributor to the rise of electric power for RC airplanes.

CONSTRUCTION

Today you can select kits, ARFs and RTFs made from a variety of
materials. Which you choose is a matter of personal taste and your
desire to work with that material during a kit build or repairing crash
damage.

Balsa wood and light plywood construction is the tried and true material
for traditional kits. You can make very light strong structures that
fly extremely well. Add heat shrink polyester film covering materials,
silk or other covering materials you can construct almost anything using
simple tools and techniques.

First plane/trainers constructed in this way are fairly resilient, but
hard hits can result in breaks that will need to be taken to the work
bench to repair. A hard crash can produce serious structural failures.

A variety of foams have become popular. EPS, expanded polystyrene is
used in cups and packing materials. Major structures are often molded
from solid foam. It is light and fairly rigid. It can take a pretty
good hit and when it does break it tends to break in large pieces. A
little 5 minute epoxy can effect repairs in the field and get the flyer
back in the air fairly quickly.

However repeated impacts can cause permanent dents and damage that must
be fixed. Accumulated impacts that might not bother a balsa plane can
start to degrade the integrity of the foam causing a loss of shape.
Again repairs can be usually effected with pieces of foam and epoxy.

There are a wide variety of kits, ARFs and RTF planes based on EPS foam.
Because most of the structures can be molded to shape, the planes can be
built very inexpensively.

Elapor is a branded product of Multiplex. EPO, expanded Polyolefin and Z foam
are similar in character. These are more damage resistant than EPS, but not as
rigid so it sometimes requires more bracing than EPS. These foams will more
likely tear than shatter as EPS does. Using the right glue, each can be fixed
quickly so that the pilot will get back into the air quickly. In balance some
feel these are a better choice for models, so this group is growing in
popularity. Each has its own special character, but all seem to be a good
compromise between rigidity, weight and damage resistance. .

EPP, expanded polypropylene is another popular foam that has been around for a
while. It moves further from EPS in that it is less rigid than the rest of the
foams. In fact EPP is quite rubbery and tends to be heavier than the other
foams. As such it needs more bracing in order to maintain a solid wing or
fuselage shape. However for damage resistance EPP is the king. I have bounced
EPP planes off of hard surfaces and sustained no damage at all.

Planes made of molded solid EPS parts tend to be heavier than balsa or
EPS structures. EPP is so resilient that it has
spawned a new class of full contact combat flying. Popular with slope
glider flyers, EPP equipped pilots will intentionally crash into each
other to try to knock each other out of the sky. Since little or no
damage will result from the crash, the pilot can just relaunch for the
next round.

Molded Polystyrene and Polyethylene are also popular. Polystyrene is the
plastic typically used in plastic model kits. And Polyethylene is the kind of
plastic used in plastic milk bottles. Like the foams, these are inexpensive to
manufacture and can be quite resistant to damage. More commonly seen in small
electric RTF planes, these are growing in popularity.

Other forms of foam and plastic are also being used in first/trainer planes.
However the ones mentioned above cover the vast majority of models out there.
Their advantage over wood is resistance to damage and ease of repair. However
wood remains popular for the light and strong structures it can produce. The
foams and plastics just open up more options for new pilots.

WHICH FORM IS MOST POPULAR?

Which you choose is up to you. If you like the idea of building with
wood, you will find a wealth of wood kit based first/beginner planes.
If you want to minimize the build, or minimize the chance of extensive
repairs, the foams may be more to your liking. And the plastics are
most typically seen in ARF or RTF packages rather than kits.

If we look at the electric plane market we see a much higher percentage
of foam and plastic planes as compared to the glow or thermal
gliders. This is especially true in the RTF part of the market. While
I have no statistics, I would guess that the sale of non-wood
first/beginner planes probably outnumber wood starters in the electric
market. That doesn't mean that the wood planes are going away just that
the market is expanding very rapidly and most of the expansion seems to
be in non-wood construction.

So, the good news is that you can have whatever you want to meet
whatever goals you set for yourself.

Channels of control - How many should you have?

Let's knock down some myths about channels and what can and can not be flown
and what can and can not be used to learn to fly. Today you can buy RC
airplanes with one channel of control and 12 or more channels of control.
They can all be flown and anyone who says they can't is wrong. Is that strong
enough?

Understand that each channel is used in some way to control the plane or some
function on the plane. From a flying point of view we will be focused on
attitude control. That is pitch, roll, yaw and speed. Broadly you can think
of them as up/down, left right and fast/slow.. This isn't correct,
but for the moment it will do. You can learn the true meaning of
pitch/roll/yaw and speed later.

The more channels of control you have, the more control you have over the
plane. Dah! However the more channels of control you have the more
responsibility you have in applying those controls. A 10 channel plane has
been designed with the assumption that the pilot knows how to use those
controls and has a sophisticated radio system to help them manage those
channels. Maybe it would be easier to learn if we had a plane that didn't
need our full understanding of 10 channels of control or a $500-$1,500 radio
system to fly it.

So how many is enough. Let's see

One - Probably Not

Two - Yes and Maybe

Glider Yes!

Many gliders are two channel. Based on their design you can have very
effective control. You can even fly wild aerobatics at speeds in excess of
100 mph. Two channel gliders can be very exciting and wonderfully enjoyable.

Typically the channels will control pitch and roll. This can be done with
elevator/rudder or elevator/aileron. With these two axis of control we can
have excellent command of the plane. Of course the plane needs to be designed
properly for the controls it has, but that will be a given here. We are not
trying to design planes.

There are hundreds of successful and effective glider designs made for slope
soaring, thermal duration soaring, hand launch, discus launch and other forms
of flying. Zagi slope wings, Gentle Lady thermal gliders, Gambler discus
launched gliders and others are examples of this kind of plane. They can be
exciting to fly and can really teach you about flying. So, when someone tells
you that you can't control a plane with only two channels, they are very
wrong! Go to the glider field or slope soaring field and you will see all
the evidence you need.

It is for this reason that many people feel the best plane to use to learn to
fly is a glider. They are typically simpler in design, lower in cost, easier
to understand and do not suffer from complicated, expensive and troublesome
power systems. You could fly for the next 20 years, have a fleet of planes
and never need more than a two channel radio. You can even enter national
competitions and win championships with a simple, low cost two channel radio
and a two channel plane.

So, two channel gliders are excellent planes to use to learn to fly. I often
recommend them.

Oh, you never thought of gliders? Maybe you should.

Two channel - Rudder/throttle control or differential thrust - maybe

If one channel is used to control the electric motor, then we can control speed
and duration of the flight. Usually these planes have been designed to climb on
power and glide down on reduced power. Rudder is used to control direction.
Planes, like the Firebird series are of this type. By placing the motor at the
right angle, the application of power will cause the plane to pitch up and
climb. What this kind of plane can not control is negative pitch. That is, you
can't push the nose down to go into a directly controlled descent or dive. This
limits your control in windy situations or where you need a more rapid descent
than gravity and glide path provide.

My personal experience with these planes are that they fly well and are easy but
they can not be safely flown in much wind by a new pilot. Since you can't dive
into the wind they are easily blown away with the pilot having little ability to
fly the plane back up-wind. If you have one, fly it in calm conditions.

An alternate design is the differential thrust models that have two motors.
These planes have no flight control surfaces. Like the example above, when you
apply full power they tend to climb and when you reduce throttle they glide
down, but you can't direct the nose down to fight the wind. These planes steer
left and right by changing the speed of the motors.

My personal experience with these is that they are even less wind worthy than
the Rudder/Throttle planes. In dead calm conditions they can be fun but
control is so limited that I can't recommend them as trainers. But they can be
a lot of laughs.

Thousands of new pilots have had their first taste of flying on these
throttle/rudder pr differential thrust planes. And you can do some pretty cool
things with them.
However, without the ability to control downward pitch, to dive into the wind,
these planes can be very easy to lose in any sort of wind, especially for the
inexperienced pilot.

Three Channel - Power - Yes

We already achieved a yes for gliders with two channels. For unpowered silent
flight, two is enough. In my opinion, when we have three channels to work
with we have enough control for the new power pilot to have a good command of
a plane with a motor. They can control pitch, roll and speed. The plane can be
managed
but the controls are still quite simple. A plane designed around this channel
count, can be a great learning platform and can carry the pilot long into the
future.

In my opinion, the most important asset we gain is the ability to push the
nose down so that we can penetrate into the wind. If you have ever seen a
glider pilot fly you know that even though he does not have a motor, he has
the able to fly down wind and to come back against the wind. This is done
through a controlled dive where the plane picks up speed so that its air speed
exceeds that of the oncoming wind and progress can be made over the ground.

Whether it is throttle/elevator/rudder or throttle/elevator/ailerons, this
plane can be controlled and therefore gives the new pilot the authority to
command the plane as he wishes. In fact very exciting planes can be made with
three channel control. They can be highly aerobatic or they can be slow
flyers that can fly indoors.

So, in my opinion with three channels we have reached the minimum channel count
for controlled powered flight. We have enough control, yet we can use very
simple and inexpensive equipment to fly the plane. A single stick radio with a
slide, lever or switch can provide all we need. I prefer proportional control
of the motor, but even with only on/off motor control you still have enough
control. However I always recommend proportional control for the motor.

For some, this will be all the control they will ever need. They can have
slow flyers, high speed aerobats, beautiful scale ships and never lack
positive control of the plane. This is where I started my flight training and
it has taken me quickly into all kinds of wonderful flying experiences.

Four or more channels. - Yes Yes

So, if three is enough, why do we need more? The answer is more channels give
us more control. While we have positive control of a three channel power
plane, we can have more positive control with four or more. Now we can have
throttle, pitch, roll and yaw control and apply them all at the same time or
any time of our choosing. This normally translates into throttle, rudder,
elevator and ailerons. This can provide more controlled landings, or make 3D
flight possible. Aerobatics can be much more sophisticated.

While 2 channel beginner gliders are very common and three channel beginner
electrics are common, glow powered starter planes are much more likely to have
four channels. Part of this is a matter of tradition and part has to do with
the nature of the plane. Glow powered starter planes are typically larger,
faster and more powerful than the typical starter electric. While the gliders
might be larger they are normally much lighter and travel at much slower
speeds.

A typical glow powered starter plane might be 5 pounds and capable of 50 mph.
It represents a lot more energy than a 3 channel 1 pound electric that is
moving along at 25 mph or a 30 ounce glider floating along at 10 mph. When you
tell that bigger faster plane to turn, you want to make sure you have as much
control
as possible.

For this reason, while I do not fly glow powered planes, when speaking with
potential new glow pilots, I normally recommend they equip themselves for a
minimum of four channels. There is no question that you can fly a glow
powered plane on throttle/rudder/elevator but you won't find many around on
the shelves of your local hobby store. Where you will see three channel glow
planes it is more likely to be in the flying wings and pylon racer designs.
However these are not your customary first/trainer planes in the glow world.

Five Plus - what are they for?

Let's just finish up with a brief overview of why you would ever have more
than 4 channels:

It is very common to put a servo on each aileron and assign them to individual
channels. Now you can trim them from the radio and you can set up different
up throws from down throws to tune the plane for less drag. Using this setup
you can also double duty the ailerons as flaps or spoilers.

Flaps are likewise often split between two channels for more flexible
control.

Less common is the split elevator that has two servos on two channels that can
be made to follow the ailerons to make the plane roll faster or perform other
stunts more effectively.

It goes on and on. It takes expensive and sophisticated radio gear to handle
some of these functions, but that cost is going down and the ease of set-up is
going up. Many beginners are now entering the hobby with computer radios as
their first radio, or their first upgrade from an initial 2, 3 or 4 channel
standard radio.

SPACE

How much space do you have for flying? If you have totally clear space of at least 600'X600',
about 9 square acres, approx 4-6 squarefootball/soccer fields, then most parkflyer class planes
should be fine. These are planes that are typically two pounds or less that typically fly at about
40 mph or less. These planes are commonly powered by Speed 400 or 480 brushed motors.
They also fly well at partial throttle so that you can fly at less than full power and have more time
to think and less rush to turn.

If your space is more like 200X200, one square acre or one football/soccer field, then a
different plane is in order. Now you want something more akin to a slow flyer. These planes
do ver well under 20 mph and some can fly so slowly that you can almost jog with them. Their
main challenge is their light wing loading and wign designs make them challenging to fly in
more than about 5 mph winds. However, for a new flyer with limited space, they make wonderful first planes.

These are my own designations and are based on my subjective
ranking of the space a new flyer should have when learning on
his own. An experienced fyer can fly faster planes in smaller spaces,
but a new flyer wants to have more space so you are not in a constant
state of panic trying to turn.

Of course you can get above the edges of the field and expand your space,
but if you lose control, you drop in woods, on top of kids or smash
someone's windshield. If that windshield is in a car is traveling
down a road when you hit the windshield, you could cause an
accident or worse.

So much for space. You get the idea.

Summary

So, if you made it this far, you should get an award! By now you should have
seen that there is no ideal best first plane. It is a myth. Many planes can be
excellent first planes.

What we have discussed are the characteristics of planes that would be better
suited for new pilots.

So, here is my mythical best first plane:

High Wing
Significant dihedral
2 or 3 channel glider
3 or 4 channel electric
Foam construction - EPP, Elapor, EPO, Zfoam or EPS foam
I love gliders and feel they make great first planes/trainers
If it is power, I think the pushers are outstanding

I hope you found some of this useful, helpful and perhaps interesting. If not,
how did you get this far?

The AMA

The AMA, the Academy of Model Aeronautics, is an outstanding resource to the
new and experienced flyer. I encourage you to become a member. Here is an
outstanding series of articles published by the AMA that will be really useful
to new pilots. It is called, "From the Ground Up" by Bob Aberle. I highly
recommend
it.http://www.modelaircraft.org/mag/FTGU/Part1/index.html

WHAT YOU NEED TO KNOW ABOUT RECEIVERS
by Ed Anderson
aeajr on the forums
Revised June 2015

Preface

Today, most radio systems are based on 2.4 GHz. Much of this article
is still valid but make note of where I am talking about 2.4 GHz systems vs.
27 or 72 MHz systems. Frequency control is very important in the 27 MHz and
72 MHz worlds but is virtually unknown when using 2.4 GHz systems. So read
in the context of what frequency system is being used.

======================================

You control the plane by moving controls on the radio, but it is the
receiver that "hears" the radio and directs those commands to the proper
servos to move them according to your wishes. So, what do you need to know
about receivers when preparing and flying your plane?

By convention all radio systems use a transmitter and a receiver. However in common
use, in the RC airplane hobby we typically refer to the thansmitter as the radio. While this
is technially incorrect, everyone knows what we mean, so I will speak of the radio and the
receiver. For those of you who are radio systems wizards, I hope you will forgive me
for this convenience.

FREQUENCY AND CHANNEL

Receivers are specific to a given frequency. For example, in North America,
NA, our planes can be flown on 27 MHz, 72 MHz, and now 2.4 GHz. Your
receiver has to match the frequency of your radio in order to be able to hear it.

In North America 2.4 GHz radios are now the most common but 72 MHz is
also considered a valid frequency for flying RC aircraft. 72 MHz is
split into 50 sub frequencies, or channels so that we
can have more than one person flying a plane at any given time.

In NA, 27 MHz is typically only seen in low end RTF planes and is shared
with low end cars and boats. 27 MHz is limited to 6 channels. Also note that
27 MHz is the frequency band used by Citizen Band radios. If you tend to fly
near a highway you may encounter interference from CB radios. While CB
radios are not as common today as they were years ago they are still out there.

For all practical purposes, 2.4 GHz is now the standard for RC systems. The
main attraction to 2.4 GHz is there is no need for frequency control, which we will
discuss later. Also, this system operates well above the frequency level of most of
the "noise" that is generated by other components in the airplane so the 2.4 GHz
systems are less likely to pick this up as interference. However because of the
very short wavelength they are more prone to having the signal blocked. More on
this later.

With non 2.4 GHz systems your receiver needs a crystal that matches the
channel of your radio. In RTF packages, this is already done, so you don't
need to worry about it. However if you are buying your own receivers, you
must match them to the frequency and channel of your radio when you buy
them. Your supplier can help you with the details. One suggestion is that
you not mix crystal brands. They may work but this introduces a risk that
you are better off avoiding. If you get a Hitec receiver, get a Hitec
crystal.

AM and FM and FM SHIFT (72 MHz)

Just like your car radio, RC radios can use AM or FM to transmit their
instructions to the plane. AM is an older technology but it is still in
use, primarily in low end 2 and 3 channel radios. However most new radios
are FM. Both work!

In North America, 72 MHz systems are grouped by those using positive shift and
those that use negative shift. Typically we speak of JR and Airtronics as
positive shift. Hitec and Futaba are negative shift. In some cases these
brands can be made to change shift through a function called shift select or
reverse shift that can be set at the radio.

Shift refers to how the radio codes instructions for the receiver. One is
not better than the other, they are just different. This is only important
when you are buying a new receiver as you need to be sure that your FM
receiver and your FM radio are using the same shift.

Crystals are not specific to shift, but they may be specific to AM vs. FM.
Be sure you get the right type of crystal for your receiver.

FM/PPM and FM/PCM (72 MHz)

PPM and PCM further define how the radio codes commands to the receiver. We
normally speak of PPM and PCM in the context of FM radio/receiver
combinations. If you are buying an AM receiver/radio, or a 2.4 GHz system you don't
need to take this into consideration.

FM receivers can be either PPM or PCM. When people say FM, they typically
mean FM/PPM. If they say PCM, they mean FM/PCM.

As long as the shift is right, you can mix brands of FM/PPM radios and
FM/PPM receivers. On the other hand, FM/PCM receivers are highly brand
specific. If you have a Futaba radio capable of PCM transmission and you
wish to use a PCM receiver, you must have a Futaba PCM receiver that is
compatible with that model radio. No mixing brands in PCM.

As far as I know, all FM radios can transmit in FM/PPM. Some can transmit
in FM/PCM also. I don't know of any that are FM/PCM only, but there may be
one out there. If PCM is listed, it is normally an extra feature, not a
requirement you use PCM.

Some will say that PCM is better and more reliable. I can neither confirm
or dispute this point as I have not done testing. I use both and have found both reliable.
I will point you to a couple of articles that discusses PCM, how it works and their opinion
of the advantages.

PCM receivers tend to be more expensive, larger and heavier. From what I
gather FM/PPM is what the overwhelming majority of flyers use. FM/PCM seems
to be most popular in the high performance world, giant scale and
competition planes. Choose whichever you like as either will fly your
plane.

RANGE

For practical purposes, range is determined by the receiver, not the radio.
It is a function of sensitivity of the receiver and its ability to pick out
the radio signal and filter out noise. Many brands state the rated range of
their receivers and some do not. I suggest you stick with brands that state
their rated range or at lest advise of their intented purpose. Otherwise you
could end up flying beyond the range of your receiver.

How much range is enough? That depends on the application. You can
NEVER have too much range, but you can have too little. If the plane
gets out of range it will crash or fly away. More range is always better.

Here are my suggestions for minimums:

Indoors

Indoor planes are usually very weight sensitive, every gram counts.
To get extremely light weigh, sometimes range has to be sacrificed but that
is OK indoors as long as you know what it is. I suggest 200' minimum and
more is better but you may be fine with less. Many indoor flying spaces are
less than 100 feet along any span and you are not going to accidentally fly
past the walls.

Outdoor

Micro planes, micro helis and small electric planes under 36" wing spans can
often get by with ultra light receivers with ranges of as little as 500
feet. This is adequate if you have a small model or fly in a small field of
under 500 feet in span. Many of these small models can be hard to see at
ranges of more than 300 feet, approximately the length of a football field.
I prefer more range, but many people do fine with 500 foot receivers.

Today there are plenty of micro receivers, sometimes called parkflyer
receivers, with 1000' rated range that are under 1/3 ounce, about 9 grams.
I have a large field that is 1600 feet long so it is easy for me to get a plane
out beyond 500 feet without realizing it. While it can become hard to see them
at that range, I don't want to lose it because I ran out of receiver range.

For 2M and larger gliders and anything with wing spans over 5 feet I recommend
a full range receiver which will typically have a range of 1 KM or more and
may be good beyond a mile.

If your receiver is rated for "line of sight" that means that as long as you
can see the model, you should be able to control it. These receivers will
be your longest range receivers. They often carry the "full range" designation.

SIGNAL PROCESSING - Single and Dual Conversion, DSP and more (72 MHz)

In addition to range, 72 MHz FM receivers will usually specify if they are single
conversion, dual conversion, or that they use some other method of signal
processing. I will leave it to the engineers to go into depth here.
However, as a general rule, dual conversion is better than single but there
are excellent single conversion receivers that have digital signal
processing and other ways of making sure they pick up the right signal.

I have no hesitation to use single conversion receivers with 2600 foot, (
1KM or .6 mile) rated ranges in my models that will be flown less than 1500
feet out. Most of my electric planes can't be easily flown further than
that and since I am operating at less than 70% the raged range I feel comfortable
that good quality single conversion receivers should be fine. This includes
my 2M sailplanes.

For my larger sailplanes I use only dual conversion receivers. Here I am flying
planes, that may be over 1/2 mile out and 1000 feet or more in altitude. I need
every bit of signal processing I can get to insure I get clean control. I can't afford
even a single glitch. If my plane is on 72 MHz I want a dual conversion system.

You make decisions based on your type of flying. This is what I do.

Some receiver brands offer single conversion, dual conversion and perhaps
other types of receivers. Be sure you get the right kind of crystal based
on the receiver. For example, Hitec dual conversion receivers and single
conversion receivers take different types of crystals. I don't know what
makes them different but you can not interchange them. They won't work.

CHANNELS (all frequencies)

We spoke of channels above in terms of frequency. We also use the word
channels to describe how many servos/devices you can control. So a 4
channel radio can control up to 4 devices. It is OK to have
more channels in the receiver than your radio has as some slots are used for
things other than channel control. For example, if we have a 4 channel
radio and are flying a 4 channel plane your slots might be used like this:

In this case you might want a 6 channel receiver to give you 6 slots. Or you
can use one or more Y cables to share slots. However I prefer to have a
receiver with extra slots rather than use Y cables. I feel it will give me
greater reliability. Rather than putting money into Y cables I would rather
put the money into the receiver.

If you have a 3 channel electric plane, you need a minimum of a 3
channel receiver. You don't typically need a separate slot for a receiver
battery as your electronic speed control normally provides the receiver with
battery power from your motor battery. You can use a 3, 4, 5, X channel
receiver, but it must have at least 3 channels.

You can also use a 2 or 3 channel receiver with a 4 or more channel radio,
but you will only have 2 or 3 channels of control available. An example
might be to use a 3 channel receiver for your R/E/T plane but use a 4
channel radio to fly it. That works!

COMPUTER RADIO AND CHANNEL MIXES
True for all radios regardless of frequency

If you are splitting functions using mixes in a computer radio your
receiver may need more channels. For example, if you have a computer
radio, you might be able to use two servos for your ailerons and have each
work from its own channel. Each aileron will be controlled its own channel.
Some radios can put the second aileron on any channel and some require they
be on specific channels. Consult your manual for guidance here.

Here is an example where we use more than one slot for a function because we
have individual servos on each surface. This is the layout of one of my
gliders and is controlled from my Futaba 9C computer radio. I use an 8
channel receiver and 7 servos.

Note that most receivers operate at 4.8 to 6 Volts though some can operate
at higher voltages. In glow, gas and gliders, this is usually supplied by a 4-5 cell NiCD
or NiMh receiver pack but can come from lithium packs with voltage regulators. In
planes using glow or gas power, or in gliders, this is a battery pack that plugs into the
receiver or into a switch that goes into the receiver. There are some new
receivers that can work on a two cell lithium pack of 7.4V. There are some tiny
receivers, made for indoor flight and micro planes that can
operate on one lipo cell at 3.7 V. Always read your
manual, but in general, never directly plug a battery pack of more than 6 volts
into your receiver unless you are sure it uses a different voltage or you will
release the "magic smoke" and the receiver will not work.

Note that your receiver might be able to operate on 7.4V, 2 cell Lipo, but your servos
may fry at that voltage so be careful about what receiver pack you use.
RTFM, read the friendly manual.

If this plane has an electric motor, the receiver will most likely get its
power from the ESC, electronic speed control. Note that even though your
flight battery might be 11.1V or higher, the ESC has a circuit that steps
this down to 5 volts to power the receiver. This circuit, called the BEC,
battery eliminator circuit, eliminates the need for a separate receiver battery.

If you look at the manual for your ESC, it probably indicates that, if you
use more than a certain voltage for your motor pack, you will need to go to
a separate receiver battery. This is because the BEC can only step the
voltage down so far. Or it may say the BEC can handle up to 4 servos on the
receiver up to a 9.6V motor battery, for example, but you are restricted to
3 servos if you go above that. After that it has to be bypassed, you need
a separate receiver pack.

There is an article on the BEC in this e-book. Be sure to read it.

Summary

The receiver is the most critical of all the electronics you will put in
your plane. The most expensive radio with the wildest features is just a
paperweight without a good receiver to carry out its instructions. While
the terms can be confusing at first, you should now be prepared to choose
a receiver with confidence. Remember to always consult your radio manual
for any specific needs of your radio system.

A key point is that it is the receiver and not the radio that really
dictates the range you can expect. I encourage you to be very aware of the
range rating of your receivers so you don't lose a plane by exceeding your
safe range.

Your receiver has to have enough channels to accept commands from your radio
and to accommodate the number of servos/devices you have in the plane.
However the number of channels in the receiver does not have to match the
number in your radio.

2.4 GHz systems and do away with many of the issues and points of consideration
for 27 and 72 MHz.

Receivers and radios are very tightly tied together. If you start with an RTF airplane
package then use the radio that came with that package and consider that radio
dedicated to that package. When you are ready to take the next step THEN you
are ready to look at making that larger investment in a "good radio". There is a chapter
later in the book on selecting your first radio. I recommend you read it before making
your first radio purchase.

We will discuss the parts of the radio system and their function. While the transmitter is the star of the show, without the other parts of the system, it can't do anything for you. So, I will briefly cover the other components of the radio system first.

I can't place photos in the article. Below are the photos. They were uploaded in the correct order.

Some of the photos in this article have been taken of my own equipment either on the bench or mounted in my planes to help you see how it all goes together. I would also like to take a moment to thank Hitec RCD USA, Inc., for providing access to their image library to help us provide additional pictures that will help illustrate the article.

PARTS OF A RADIO SYSTEM
(photos referenced below)

First we have examples of two radios. One is a dual stick, typical of radios with four or more channels. The other is a single stick typical of two to three channel radios.

Next is a photo of three servos. The top is a Futaba standard size servo, the middle is a Hitec micro servo and the bottom is a GWS sub micro servo. I selected these three to illustrate the range of servo sizes. In this group, each servo is about half the size and weight of the one above it.

Next we see an electronic speed control, an ESC, which would be used to control an electric motor in an e-glider. Pure sailplanes and fuel powered planes would not have an ESC.

In the next photo we see the interior of one of my planes, a Great Planes Spirit, showing two servos, the receiver, a switch and the battery as they are mounted in the plane. Note that the battery is wrapped in Velcro, which is glued into the plane to hold the battery in place. Likewise the servos are mounted with screws and the receiver is secured with double-sided tape on the bottom.

The white control arms on the servos will be connected to rods that operate the rudder and elevator. You can see one of the rods, which is yellow, on the top and to the left of the servos. The receiver antenna runs down the interior of the plane and exits at the rear so that it is fully extended for best reception. This is a typical set-up for a beginner plane. Add a radio, connect and adjust your surfaces, balance the plane and you are ready to fly.

Here is another installation. This one is in my Zagi slope glider. This is a flying wing. You will see in the photo that the components are embedded into the foam of the wing. At the top is the green battery, then you see two standard size servos, one to either side. Finally in the center you see the receiver.

The wires have not been finally connected in this photo. The 72 MHz antenna runs through a tube that is embedded in the right side of the wing and exits at the wing tip where the antenna wire hangs lose. In this kind of plane, the electronics are sealed in with the reinforcing tape and covering.

This photo shows the wing finished. Notice the control rods that connect from the servos to the elevon control surfaces. Note the switch, which sticks out through the covering for access. The receiver and the battery are completely buried.

Let's take a look at each component and its function.

The Receiver

The receiver captures the signal from the transmitter, decodes it and uses that information to control the other parts of the radio system. The important thing to know for now is that the receiver needs to be matched to the transmitter for them to work together, though in some cases they don't have to be the same brand. They do have to be on the same frequency or channel. You can get more detail in the articles on receivers, a different chapter of this e-book.

In the photo below you will see two holes in the center of a typical 72 MHz receiver. Receivers on 72 MHz require a crystal to set the sub frequency within the 72 MHz band, similar to having channels on your TV set. This is where the crystal is installed that will designate the channel for the receiver. On 2.4 GHz radio systems there are no crystals.

Note that in RC flying, if we are using a 2.4 GHz radio system we talk about the channels on the receiver. If we are using a 27 or 72 MHz radio system we use the word channel in two ways, which can be confusing. We use channel to describe the sub frequency of the radio/receiver combination. We also use channel to describe how many devices the transmitter/receiver can control. They are completely different and the use of the same word for both in unfortunate. We will discuss more about channels later.

You also see in the photo the pins on the right where the various components plug into the receiver. Here you plug in your, servos, ESC or some other accessory pieces. The receiver shown is a six channel receiver so it can manage up to six devices under the direction of a transmitter if the transmitter is able to transmit on 6 channels. We can still use this receiver if your transmitter that has more or less than 6 channels

Frequency Bands

Today new transmitter/receiver systems are almost exclusively on 2.4 GHz. The radio system takes care of insuring there is no conflict with other RC radio systems. If you are using older equipment, 27 MHz or 72 MHz, the transmitter and receiver must be on the same frequency band and on the same channel within that band. The pilot must follow "frequency control procedures" to insure that no other flyer is on the same channel or the radio systems will come in conflict and the planes will crash.

Range

One important thing you need to know about receivers is that the receiver is usually the part of the radio system that determines the effective working range. I discuss receivers in more depth in another article, but the fact that the receiver determines range should show you that you need to consider what receiver you are using in each application. If your receiver does not have enough range, you could fly beyond its capabilities, resulting in a crash.

I bring this up because some receivers have working ranges of as little as 100 feet while others have ranges in excess of a mile. Therefore you must be sure the receiver you are using is appropriate to your application.

Servos

Servos contain motors that are used to make things move in the plane. They will be connected to the rudder, the elevator, the ailerons, the flaps and other things in the plane that need to be moved to make them operate. Servos come in a wide range of sizes and strengths. We will want to match the servo to the job to be sure it is strong enough, can fit in the space available and be no heavier than necessary as excess weight on a plane is a not good.

A simple 3 channel electric plane will have two servos that manage the pitch and roll functions while the electronic speed control manages the throttle. More complex models may require six or more servos. We won't get into servos to any degree here except to say that the servos plug into the receiver and respond to instructions sent from the transmitter to the receiver. Unlike the receiver, virtually all servos work with all receivers as long as the plugs match; and most do. If you are buying new servos with universal plugs, you can readily mix and match brands with little likelihood of a problem.

Batteries

Your radio system works on electricity, which is supplied from a battery pack that is made up of cells, usually rechargeable cells. Nickel Cadmium, NiCd, Nickel Metal Hydride, NIMH, and Lithium Polymner, LiPo, are the most common rechargeable cells used in our airplanes.

NiCd have the lowest power to weight ratio while Lithium cells have the highest of the ones mentioned here. As a result Lithium and specifically LiPo packs are growing in popularity.

Whatever cell types you use make sure you use a charger that specifically works with that battery type. Charging with the wrong type of charger can damage the cells or lead to a fire. Make sure you have the right type of charger.

There will also be a set of batteries in the transmitter. If your radio system uses rechargeable batteries, the package may include a battery charger that plugs into the wall and charges the radio. There are more sophisticated chargers available, but for most people these simple chargers work just fine for their transmitter batteries.

The Switch

Most electric planes do not have switches. You power them on by connecting the battery. When you are finished with that pack, you disconnect it and remove it for charging. Note that if you leave the battery connected, there will be a constant flow of power to the speed control. This will drain your battery pack. If the pack is NiCd or NiMh, little damage will occur. If the battery is Lithium, this may destroy the battery pack.

Electronic Speed Control - ESC

As covered in an earlier article, the device that controls the motor is called the ESC or electronic speed control. Typically there will be wires that go to the motor, wires to the battery and wires to the receiver so the ESC can distribute power to the receiver, and respond to commands from the transmitter to control the speed of the motor.

multiplex speed control.jpg

Accessories

There are lots of other things that can hook into the receiver and become part of the radio system. Things like altimeters, lost plane locators, battery monitors and the like. However they are not core to the operation of the plane.

The Transmitter

Finally we get to the star of the show, the transmitter. This is the part of the radio system you hold in your hands. It has those lovely sticks and switches and things that allow you do what you need to do to fly a plane that is hundreds or thousands of feet away while you are standing there on the ground.

Transmitters come in a wide variety of prices and capabilities. Of all the investments you will make in getting started in RC flying, your radio transmitter is one of the most important. Which radio you select will determine how easily you can set-up your plane, how easily you can adjust and trim it and how complex a plane you can fly.

I divide transmitters, typically called radios, into two groups, standard and computer radios. Standard radios retain the settings for the currently flown plane. If you want to use that radio to fly a different plane you must manually make adjustments to match the new plane. With computer radios, you can store the settings for many planes in what we call model memories. You select the plane you want to fly from a menu and the radio resets everything to match that model. There are many other features that computer radios bring to the hobby, but for the moment this one feature adequately separates computer from standard radios.

Like all areas of electronics, new models come out often, with each having more features and usually delivering those features at lower prices than the previous generation. Features that were only available in high end systems just a few years ago, like elevon and V tail mixing, are now standard features on some of the lowest cost radio systems on the market.

Budget

For most people budget will be the determining factor in what radio system they buy. Let me say here that you can get a quality four channel radio for under $50 that will fly any of the typical starter electric planes. However, as you will see, there are many more capable radios that are worth your consideration. They offer convenience and higher degrees of control and can handle more complex planes. Depending on where you plan to go in this hobby, a larger up front investment may be money well spent.

One of the things that confused me when I first started flying RC airplanes was this business of channels.

When using radios based on 27 MHz, 72 MHz and many other frequencies, channels can refer to the operating frequency of the radio. As stated above, it is critical to know the channel so that the transmitter and receiver can be placed on the same channel. Channel matching is usually done by inserting a crystal into the receiver so that the receiver matches the channel of the transmitter. This does not apply to Radio systems on 2.4 GHz.

Channels can also refer to the number of functions the radio system can control in the plane. We speak of three channel airplanes, four channel airplanes and more channel airplanes. Today you can buy radios that can provide 18 or more channels of control. What you would do with all those channels depends on the plane, but it is enough to say that for some applications, even 18 channels may not be enough.

In the United States, radio frequencies and their uses are regulated by the Federal Communications Commission, the FCC. The FCC has designated the 2.4 GHz and 72 MHz band as the primary recognized frequency range for model aviation. Please don't buy a radio on 75 MHz as that is designated for ground use such as cars and boats. The 2.4 GHz and 72 MHz standard is also recognized by Canada;s regulatory organization.

If you are considering buying a plane that uses a 27 MHz radio system you must be especially alert because 27 MHz is also used for low end cars and boats. That kid with the RC car could be on 27 MHz and on your channel. So keep an eye out for other RC uses and always speak to anyone using an RC device to be sure there will not be a conflict. 2.4 GHz does not have this problem.

CHANNELS OF CONTROL

The second use of the word channel in relation to radio systems has to do with how many channels of control they provide. A three-channel radio can control three devices on the plane. A six-channel radio can control six devices, and so on.

Some channels are proportional which means as you move the stick, dial or lever, the device is controlled in a proportional fashion. Move the stick left a little bit, the rudder moves left a little. If you move it a lot, the rudder moves a lot. That is proportional control.

Other controls have definite positions. For example the landing gear switch is either up or down. There is no half way. Some channels are controlled by switches, which might have three positions to designate three conditions such three different positions of the flaps.

If we look at the common starter electric planes most require only three proportional channels of control. You need pitch and roll in order to manage the plane in the air. Add to that a throttle channel.

In general, you can fly almost any model airplane with a four channel radio. That allows you to manage elevator, rudder, ailerons and throttle, for a powered airplane.

Radios with more than four channels provide greater flexibility. A six channel radio can add the control of landing gear and flaps. If you had more channels you could control smoke, lights, and other things on the airplane.

Let me leave the topic of channels on this note. You can buy radios with two channels and you can buy radios with twelve channels, and every step in between. What you buy will be determined by what you need, what you plan to do, and how much money you have to spend.

My usual advice is, if you start with an RTF airplane package then use the radio that came with that package and consider that radio dedicated to that package. When you are ready to take the next step THEN you are ready to look at making that larger investment in a "good radio". There is a chapter later in the book on selecting your first radio. I recommend you read it before making your first radio purchase.

PRICES AND PACKAGING

Before we can talk about prices of radios we need to be aware that radio systems are typically packaged in several ways. You can buy the radio alone, or you can get it with the receiver and it is very common to also include some number of servos. In some packages there may be a switch and a set of batteries and perhaps some servo extension wires. When you are looking at prices for radios be sure you know what is included.

Some package deals may be nicely priced for what you get, but may include components you canâ€™t use. For example the package may include standard size servos and your plane may call for micro servos. If you really don't need those standard servos you can put them aside for use in a future plane, or you might be better off buying the radio alone and getting the rest separately. However, if the components are right, it is more convenient and often more cost effective to by it all as a package.

WHICH BRAND IS BEST FOR YOU?

There are many brands of radios. The big names in our hobby are Hitec, Futaba, Airtronics, JR and Spektrum. However there are many other brands of radios and many of the smaller brands are very good. There are also private labeled radios that are actually made by these major manufacturers under private label agreements. If you stay with these top five you can be pretty confident of getting good quality products with good service to back them. However if another brand is popular at your club and the clubs experience is good, don't be afraid to stray from the big five. The experience of your fellow flyers is a valuable guide.

In fact, many people will tell you that the best brand and model for you is the one or two that are most common in your club. If you get one of these there will be many people who can help you with their use. The assistance of a fellow flyer at the field can be extremely valuable so don't overlook this factor. There can be safety in numbers and convenience in using the same type of radio that everyone else is using.

STANDARD VS COMPUER RADIOS

In the olden days of as little as 20 years ago, there were standard radios and computer radios and the cost differences were huge. Standard radios had 2-6 channels of control, trim slides and perhaps not much more. If you needed to reverse a servo you remounted it or used a servo reversing adapter. If you needed special mixes for V tail planes you had to buy devices to put in the plane to create the mix.

Features like servo reversing and end point adjustment were later added to these standard radios. They did a good job, but were set-up to fly one plane. It ws common for pilots to have one radio for each plane so they could set it to the specifics of that plane and leave it that way. You could reset for each plane but this was troublesome and error prone.

Along came computer radios and the ability to store multiple model's settings in the radio. Now one radio could be used to fly many planes. In addition the radio could do channel mixing inside and transmit it to the receiver directly. You could mix channels together to manage V tail planes or elevons for flying wings. You could also control how far the servos would turn which is a great way to get the right amount of throw in your control surfaces. This was heaven, but it was expensive.

However if you buy a new radio today many of the least expensive radios will allow you to reverse a servo from the radio and include V tail and elevon mixing, and some even include end point adjustments to help you set the movement of your control surfaces. These were features that were common to the high end computer radios. Now they are appearing in the basic radios so every year you get more for your money.

However only the computer radios can store the settings for multiple airplanes. For many this is their most important feature.

Summary

So, that wraps up our discussion of radio basics. While we covered a lot, there is a lot more we could have discussed, but my fingers grow tired from typing and you need to take a break from reading. Ask your questions, make your statements and share you knowledge. It will make this all the more fun for all of us.

Last edited by aeajr; 06-10-2015 at 10:54 AM.
Reason: updating the article to keep it current.

Since this e-book is focused on electric flight, I thought it would be appropriate to put something in about the AMA membership program developed specifically with electric pilots in mind. At half the price of regular AMA membership, it seems to offer a nice package for pilots who are not interested in larger planes, glow planes, gas planes or jets.. If you are primarily focused on small electrics, electric helies or small gliders, this is something you should consider.

In addition, the AMA is looking to help form Park Pilot clubs and help those clubs establish Park Pilot fields. These clubs would be focused on flying park flyers and would not be open to gas, glow, jets or large planes. As a result they can be located in smaller fields and potentially in places where regular AMA fields have been rejected or cast out.

Certianly sounds interesting.

Park Flyer Definition:

Park Flyer models will weigh two pounds or less and be incapable of reaching speeds greater than 60 mph. They must be electric or rubber powered, or of any similar quiet means of propulsion, including gliders. Models should be remotely controlled or flown with a control line, remain within the pilotâ€™s line of sight at all times, and always be flown safely by the operator.

The AMA is encouraging the development of new, officially recognized AMA Park Pilot sites in metro areas throughout the US. As an aid in reaching this goal, weâ€™ve developed a special â€œHow to Start a Park Flying Siteâ€ turnkey package so members who are trying to secure a field wonâ€™t have to start from scratch when they approach landowners or officials responsible for regulation of public facilities. The package includes a DVD to show landowners and park officials what park flying is all aboutâ€“â€“and how different it is from the engine-powered, radio-control flying with which they may already be familiar. There are tips on how to approach officials and landowners, plus instructions on how to set up a field. It even includes a guide for how to quickly and efficiently organize a club, its bylaws, and field rules. And best of all, members will be able to inform landowners and officials that theyâ€™d be covered by AMA site liability coverage in the amount of $2.5 million, which should serve as a great incentive. The goal is to make it easier for official AMA recognized flying sites to be developed quickly and in great numbers.

If you have a question, by all means ask as others will have the same question.

Whether it is throttle/elevator/rudder or throttle/elevator/ailerons, this
plane can be controlled and therefore gives the new pilot the authority to
command the plane as he wishes. In fact very exciting planes can be made with three channel control. They can be highly aerobatic or they can be slow flyers that can fly indoors.

For some, this will be all the control they will ever need. They can have slow flyers, high speed aerobats, beautiful scale ships and never lack positive control of the plane. This is where I started my flight training and it has taken me quickly into all kinds of wonderful flying experiences.

This normally translates into throttle, rudder, elevator and ailerons. This can provide more controlled landings, or make 3D flight possible. Aerobatics can be much more sophisticated.

It's the opinion of the 'world class' instructor in the FS One Flight Simulator training program that every beginner needs to first learn aileron control before learning rudder control. This seems to make some sense for a couple reasons. 1) Elevator and aileron are combined on the same control stick. 2) Whether pylon racing, combat flying, learning some basic aerobatics or flying in a smaller park aileron control has its advantages. Yet many of us are under the impression that a beginner should learn 3-channel throttle, elevator and rudder control before advancing to 4-channel throttle, elevator, rudder and aileron control.

A foamy thread at RCU discusses what seems to be a most practical 3-channel electric aileron foamy(fixed rudder) that could be one of the best trainers for the money for a beginner. With the wide array of model planes on the market why, oh why isn't one like this to be found? [link]http://www.qnet.com/~skif/plane.html[/link]

Why doesn't HobbyZone offer a similar RTF? Hobby-Lobby has a vast selection from which to choose from a beginner pilot to an elite pilot, yet not one of their many choices is to be found like the one in the above link(a beginner 3-channel foamy plane with one or two ailerons and a fixed rudder? It's a simple enough design that could be easily manufactured with a good enough profit margin. The only difference is that instead of the servo controlling a rudder it's controlling the aileron.

So my question is why the emphasis by manufacturers on 3-channel rudder instead of 3-channel aileron and your reference above to rudder control preceeding aileron control. Another way of phrasing my query would be to say, Why wouldn't a 3-channel SuperCub with one or two aileron control surfaces (with a fixed rudder) be a better trainer for a beginner with the option of upgrading it to 4-channel with rudder control? Does it boil down to the fact that it's less expensive to manufacture a model airplane with rudder control than incorporate even one aileron into the main wing? How much more do you think it would cost to manufacture a 3-channel aileron SuperCub with fixed rudder. Isn't it their responsibility to also educate us as to the preferred learning sequence instead of just producing a plane as inexpensively as possible.

I suspose if I called HobbyZone customer support they would tell me that its more important to have rudder control than aileron control if you can only have your choice of one or the other. Who do we believe--a world class instructor or Horizon Hobby and our LHS?

When you write your book donât be too cautious about going against some of the prevailing winds of RTF electricity. I hope Iâm not beating a dead horse, chasing the wind, or wasting your time. A book about everything you wanted to know, but didnât even know what questions to ask is needed. A common sense fun to read book incorporating what to avoid and how to make it the most enjoyable experience from the get-go. Donât want to overwhelm them with a million choices as that is already one of the problems. Keep it simple while supplying them with insightful wisdom that will save them time, money, and frustration from a pedal to the metal speed mentality. Approach it from a professional manner, but make it enjoyable to a wide audience whether 12 years old or 62 years old.

The following observation is from surfing RC websites and my own newbie experiences over the past 11 monthsâspecifically â3-channel RTF electrics.â A flight training instructor (first recognized for his signature Knife Edge maneuvers and winner of the 1998 coveted TOCâTournamentOfChampions) doesnât teach rudder control(except for runway steering) in any of the basic flying lessons included in the FS ONE Simulator. His preference for the three most important channels for any beginner to concentrate on FIRST learning(once in the air or when hand launching) are throttle/elevator/aileron. He introduces his basic lessons by telling the viewers that they need to learn aileron control before rudder control. Itâs only in the advanced lessons of 3D (snap rolls, knife edge slides, etc) that this top flight instructor introduces the viewer to rudder control (4-channel).

The reason I didnât buy a 3-channel RTF SuperCub(even though the LHS thought I should) as my first plane was because it didnât have ailerons. I thought I could save some money in the long run by buying the Aerobird Swift(3-channel RTF throttle/elevator/aileron) and the Stryker 27C(3-channel t/e/a) even though they are marketed for intermediate pilots. Everyone thinks theyâre above average and besides I thought after several flights or after a few months Iâd be an intermediate. I bought both planes as much for my son as myself so the generic plain Jane SuperCub didnât look as appealing as the Aerobird Swift and Stryker. I thought the Stryker would be more enjoyable for my son to fly. He tried flying the Stryker on the FS One Simulator, but kept crashing and so we decided to just go for the gusto. Well, you can probably guess what happened. A common train of thought among the jet set seems to beââIf you havenât crashed lately you must be doing something wrongâ so I just accepted our unfortunate experience as a part of the learning curve.

Critterhunter has a thread about how to make a bullet proof Stryker, and the official Stryker thread(s) with thousands of replies is a testimony to a prevalent pedal to the metal speed mentality. I find it interesting that Critterhunters latest thread in the FoamyForum is about building a one aileron fixed rudder foamy from scratch. This affordable plane looks to be the âperfect aileron trainerâ that has eluded our never-ending quest for a consensus on an affordable aileron electric trainer that can take some abuse and keep on ticking without ticking us off. Here is the linkâ[link]http://www.qnet.com/~skif/plane.html[/link] I canât help but wonder if this is that elusive electric 3-channel aileron trainer the majority of us should have first crashed, repaired, modified and cut our teeth on before we ever gave in to our burning desire for a Stryker or some other cool colorful looking bird. Enquiring minds would like to know if Critterhunter finally got feedup repairing, modifying, repairing, modifying, âŚ his Stryker to the point that he is now going back to the basics and building the kind of plane that for many a newbie would have been much better than the one that caught their eye or the eye of the person that got them interested in the hobby. Why doesnât HobbyZone, ParkZone, Hobby-Lobby, or any company in the WholeWideWorld market a RTF 3-channel throttle/elevator/aileron(1or2) electric foamy???

Whether it was me or other contributors to these electric forums many of us jumped in and bought a plane that was probably money that should have been spent on a RTF 3-channel t/e/a electric foamy trainer, except there isnât a readily available supply, if one even exists. Isnât this the primary reason why forum after forum we have a continous barrage of newbies and others wondering/opinonating whatâs the better 3-channel RTF electric trainer for the money. And even more perplexing/troublesome is the engraining preponderance that 3-channel RTF aileron electrics are only for more advanced pilots and that beginners need to master rudder control before aileron.

What Iâm noticing in some of these forum threads is that some are going back to the basics and find more enjoyment flying a plane like an EasyStar after experiencing too many crashes and hours spent repairing and modifying a plane like an Aerobird Swift or Stryker. Itâs now apparent to me that a brushless SuperCub with ailerons and a fixed rudder would be a very suitable aileron trainer with the option to someday upgrade it to 4-channel t/e/a/r. Unfortunately, it costs more to manufacture a 3-channel RTF aileron foamy, but the irony is that we all spend/waste money on some of these planes that we later discover was money that could/should have been spent more wisely. And for quality at a reasonable price it doesnât get any better thenâMade In China. The irony is that for decades model enthusiasts could afford more expensive 4-channel glow/gas planes, and they didn't have to rely on plastic money.

The SPAD concept and the simplicity of Critterhunters commonsense homebuilt aileron plane(about as inexpensive as it get) is one of those ironies that are simply too practical. Itâs a sad commentary on the world of RTF electrics that there isnât a relatively inexpensive 3-channel RTF aileron foamy trainer available in every LHS in America. Itâs also a sad commentary on our own haste makes waste rush for the Glitz&Gusto. Flying model airplanes(made in China) and all the technology that comes with it doesnât have to cost an arm and a leg. If most of us were to take an inventory of all the money weâve spent on this hobby, and go back and spend it again weâd be able to buy a plane and flying accessories that we probably now only dream about someday owning.

It's the opinion of the 'world class' instructor in the FS One Flight Simulator training program that every beginner needs to first learn aileron control before learning rudder control. This seems to make some sense for a couple reasons. 1) Elevator and aileron are combined on the same control stick. 2) Whether pylon racing, combat flying, learning some basic aerobatics or flying in a smaller park aileron control has its advantages. Yet many of us are under the impression that a beginner should learn 3-channel throttle, elevator and rudder control before advancing to 4-channel throttle, elevator, rudder and aileron control.

...................................

So my question is why the emphasis by manufacturers on 3-channel rudder instead of 3-channel aileron and your reference above to rudder control preceeding aileron control. Another way of phrasing my query would be to say, Why wouldn't a 3-channel SuperCub with one or two aileron control surfaces (with a fixed rudder) be a better trainer for a beginner with the option of upgrading it to 4-channel with rudder control? Does it boil down to the fact that it's less expensive to manufacture a model airplane with rudder control than incorporate even one aileron into the main wing? How much more do you think it would cost to manufacture a 3-channel aileron SuperCub with fixed rudder. Isn't it their responsibility to also educate us as to the preferred learning sequence instead of just producing a plane as inexpensively as possible.

Swift,

You ask an excellent question. Let us explore it, for it is worth discussing.

The key factor is this, the lack of an instructor.

The instructor you quote assumes that the student has an instructor. Quite a reasonable assumption for an instructor. And, under the guidance of an instructor, especially if combined with a buddy box, I would agree with him completely.

However, the parkflyer explosion has been based on NOT having an instructor. And so, the design of the planes are based on the premise that the new pilot will have no help. Stability and self recovering characteristics are the key design goals. Let the new flyer release the stick and the plane will self recover, assuming it has enough altitude.

If you look at the designs, many are basically motorized gliders. Roll is induced not by ailerons but by dihedral/yaw coupling. While this gives you less control than ailerons, it is highly self righting. The plane wants to level itself, by design.

In addition, the designs are heavily weighted to stable slow flight. Many have undercambered wings and the balance are flat bottom wings.

Combine extreme stability with good slow flight character and you have a plane that is incredibly easy to fly with little input from the pilot. In fact, the greatest problem most new flyers have is over control. Having instructed many new pilots, the first thing I show them is that these planes fly very well without their interference. In fact many of these planes have a beginner mode and an advanced mode. Typically the beginner mode, usually some kind of enhanced low rate resists the urge to over control.

This could go on for quite a while, but I believe you will see the point. I do not disagree with your instructor for as an instructor he has every right to choose his manner of instruction. But when there is no instructor, design can be used to help the new pilot gain his wings on his own.

And, frankly, for many the flight characteristics of the three channel R/E/T planes are exactly what they want and what they enjoy. And what is wrong with that?

I should note that in addition to being an electric pilot and an instructor, I am also a glider pilot. The classic two channel glider, R/E only, is one of the best flying thermal duration designs that one can use. What it lacks in precision control it makes up in stability allowing the pilot to fly such a ship at great distances. I have had a 2 meter glider out in excess of 1/4 mile and in excess of 1000 feet in altitude with complete confidence that the plane would seek level on its own. With a 3 meter of this design it would be possible to fly further and higher with nothing more than the energy in the air to carry it.